Can not add Page Sections

Problem/Motivation

I can not add page sections. It gives the following error:
TypeError: Argument 2 passed to Drupal\d_p\Plugin\Field\FieldWidget\SettingsWidget::processCustomThemeElements() must be an instance of Drupal\d_p\Plugin\Field\FieldWidget\object, instance of stdClass given, called in /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/custom/d_p/src/Plugin/Field/FieldWidget/SettingsWidget.php on line 215 in Drupal\d_p\Plugin\Field\FieldWidget\SettingsWidget->processCustomThemeElements() (line 348 of /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/custom/d_p/src/Plugin/Field/FieldWidget/SettingsWidget.php)

Steps to reproduce

1. Download the default Droopler 8.x-2.2 package from https://www.drupal.org/project/droopler → (the package downloaded is https://ftp.drupal.org/files/projects/droopler-8.x-2.2-core.tar.gz).

2. Install as usual (not using composer). Install optional demo data. Everything goes ok with the installation. You can check in prueba.sionpadres.org

3. In the start page, I edit the home page. I go to "Page Sections". There, I try to use the button below the existing sections to add a new one. When I click in one of the options, the icon with the clock and "Please wait..." appears, then nothing happens. I tried with all of the different options for page sections.

4. In Recent Log Messages the following error appears each time I try to add a section:
Location http://prueba.sionpadres.org/node/10/edit?_wrapper_format=drupal_ajax&aj...
Referrer http://prueba.sionpadres.org/node/10/edit
Message
TypeError: Argument 2 passed to Drupal\d_p\Plugin\Field\FieldWidget\SettingsWidget::processCustomThemeElements() must be an instance of Drupal\d_p\Plugin\Field\FieldWidget\object, instance of stdClass given, called in /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/custom/d_p/src/Plugin/Field/FieldWidget/SettingsWidget.php on line 215 in Drupal\d_p\Plugin\Field\FieldWidget\SettingsWidget->processCustomThemeElements() (line 348 of /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/custom/d_p/src/Plugin/Field/FieldWidget/SettingsWidget.php)

There are no other error messages.

5. The same error appears in another site I upgraded from a previous droopler 8.x-2.0 installation. Up to that time, it was working fine.
------------------------------------

The complete error message is:
TypeError: Argument 2 passed to Drupal\d_p\Plugin\Field\FieldWidget\SettingsWidget::processCustomThemeElements() must be an instance of Drupal\d_p\Plugin\Field\FieldWidget\object, instance of stdClass given, called in /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/custom/d_p/src/Plugin/Field/FieldWidget/SettingsWidget.php on line 215 in Drupal\d_p\Plugin\Field\FieldWidget\SettingsWidget->processCustomThemeElements() (line 348 of /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/custom/d_p/src/Plugin/Field/FieldWidget/SettingsWidget.php)
#0 /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/custom/d_p/src/Plugin/Field/FieldWidget/SettingsWidget.php(215): Drupal\d_p\Plugin\Field\FieldWidget\SettingsWidget->processCustomThemeElements(Array, Object(stdClass))
#1 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Field/WidgetBase.php(344): Drupal\d_p\Plugin\Field\FieldWidget\SettingsWidget->formElement(Object(Drupal\d_p\Plugin\Field\ConfigurationStorageFieldItemList), 0, Array, Array, Object(Drupal\Core\Form\FormState))
#2 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Field/WidgetBase.php(211): Drupal\Core\Field\WidgetBase->formSingleElement(Object(Drupal\d_p\Plugin\Field\ConfigurationStorageFieldItemList), 0, Array, Array, Object(Drupal\Core\Form\FormState))
#3 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Field/WidgetBase.php(113): Drupal\Core\Field\WidgetBase->formMultipleElements(Object(Drupal\d_p\Plugin\Field\ConfigurationStorageFieldItemList), Array, Object(Drupal\Core\Form\FormState))
#4 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Entity/Entity/EntityFormDisplay.php(178): Drupal\Core\Field\WidgetBase->form(Object(Drupal\d_p\Plugin\Field\ConfigurationStorageFieldItemList), Array, Object(Drupal\Core\Form\FormState))
#5 /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/contrib/paragraphs/src/Plugin/Field/FieldWidget/InlineParagraphsWidget.php(664): Drupal\Core\Entity\Entity\EntityFormDisplay->buildForm(Object(Drupal\paragraphs\Entity\Paragraph), Array, Object(Drupal\Core\Form\FormState))
#6 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Field/WidgetBase.php(344): Drupal\paragraphs\Plugin\Field\FieldWidget\InlineParagraphsWidget->formElement(Object(Drupal\entity_reference_revisions\EntityReferenceRevisionsFieldItemList), 7, Array, Array, Object(Drupal\Core\Form\FormState))
#7 /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/contrib/paragraphs/src/Plugin/Field/FieldWidget/InlineParagraphsWidget.php(844): Drupal\Core\Field\WidgetBase->formSingleElement(Object(Drupal\entity_reference_revisions\EntityReferenceRevisionsFieldItemList), 7, Array, Array, Object(Drupal\Core\Form\FormState))
#8 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Field/WidgetBase.php(113): Drupal\paragraphs\Plugin\Field\FieldWidget\InlineParagraphsWidget->formMultipleElements(Object(Drupal\entity_reference_revisions\EntityReferenceRevisionsFieldItemList), Array, Object(Drupal\Core\Form\FormState))
#9 /home2/xxxx/domains/prueba.sionpadres.org/profiles/droopler/modules/contrib/paragraphs/src/Plugin/Field/FieldWidget/InlineParagraphsWidget.php(955): Drupal\Core\Field\WidgetBase->form(Object(Drupal\entity_reference_revisions\EntityReferenceRevisionsFieldItemList), Array, Object(Drupal\Core\Form\FormState), NULL)
#10 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Entity/Entity/EntityFormDisplay.php(178): Drupal\paragraphs\Plugin\Field\FieldWidget\InlineParagraphsWidget->form(Object(Drupal\entity_reference_revisions\EntityReferenceRevisionsFieldItemList), Array, Object(Drupal\Core\Form\FormState))
#11 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Entity/ContentEntityForm.php(125): Drupal\Core\Entity\Entity\EntityFormDisplay->buildForm(Object(Drupal\node\Entity\Node), Array, Object(Drupal\Core\Form\FormState))
#12 /home2/xxxx/domains/prueba.sionpadres.org/core/modules/node/src/NodeForm.php(127): Drupal\Core\Entity\ContentEntityForm->form(Array, Object(Drupal\Core\Form\FormState))
#13 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Entity/EntityForm.php(149): Drupal\node\NodeForm->form(Array, Object(Drupal\Core\Form\FormState))
#14 [internal function]: Drupal\Core\Entity\EntityForm->buildForm(Array, Object(Drupal\Core\Form\FormState))
#15 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Form/FormBuilder.php(532): call_user_func_array(Array, Array)
#16 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Form/FormBuilder.php(371): Drupal\Core\Form\FormBuilder->retrieveForm('node_content_pa...', Object(Drupal\Core\Form\FormState))
#17 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Form/FormBuilder.php(629): Drupal\Core\Form\FormBuilder->rebuildForm('node_content_pa...', Object(Drupal\Core\Form\FormState), Array)
#18 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Form/FormBuilder.php(321): Drupal\Core\Form\FormBuilder->processForm('node_content_pa...', Array, Object(Drupal\Core\Form\FormState))
#19 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Controller/FormController.php(91): Drupal\Core\Form\FormBuilder->buildForm(Object(Drupal\node\NodeForm), Object(Drupal\Core\Form\FormState))
#20 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch))
#21 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array)
#22 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/Render/Renderer.php(573): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#23 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#24 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)
#25 /home2/xxxx/domains/prueba.sionpadres.org/vendor/symfony/http-kernel/HttpKernel.php(151): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#26 /home2/xxxx/domains/prueba.sionpadres.org/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#27 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#28 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#29 /home2/xxxx/domains/prueba.sionpadres.org/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#30 /home2/xxxx/domains/prueba.sionpadres.org/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#31 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#32 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#33 /home2/xxxx/domains/prueba.sionpadres.org/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#34 /home2/xxxx/domains/prueba.sionpadres.org/core/lib/Drupal/Core/DrupalKernel.php(708): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#35 /home2/xxxx/domains/prueba.sionpadres.org/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#36 {main}