A transaction named mimic_implicit_commit is already in use

I tested ginvite today. I were able to do the registration process for the first test user.
I think, it was already for the second where the registration stopped working with a postgres error after clicking on register link within email and trying to save form on /user/register?invitee_mail=a2FpLmZyZWNoQGRpcmVjdGJveC5jb20

The website encountered an unexpected error. Try again later.

Drupal\Core\Entity\EntityStorageException: A transaction named mimic_implicit_commit is already in use. Active stack: 674984ea6abce6.13306750\drupal_transaction > 674984eaabbfc9.84182019\savepoint_1 > 674984eaafb1b1.26828222\mimic_implicit_commit in Drupal\Core\Entity\Sql\SqlContentEntityStorage->save() (line 817 of core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php).
Drupal\pgsql\Driver\Database\pgsql\Connection->startTransaction() (Line: 429)
Drupal\pgsql\Driver\Database\pgsql\Connection->addSavepoint() (Line: 149)
Drupal\pgsql\Driver\Database\pgsql\Schema->queryTableInformation() (Line: 35)
Drupal\pgsql\Driver\Database\pgsql\Upsert->execute() (Line: 312)
Drupal\Core\Cache\DatabaseBackend->doSetMultiple() (Line: 227)
Drupal\Core\Cache\DatabaseBackend->setMultiple() (Line: 215)
Drupal\Core\Cache\DatabaseBackend->set() (Line: 133)
Drupal\Core\Cache\VariationCache->set() (Line: 172)
Drupal\flexible_permissions\ChainPermissionCalculator->calculatePermissions() (Line: 39)
Drupal\group\Access\GroupPermissionCalculator->calculateFullPermissions() (Line: 40)
Drupal\group\QueryAccess\GroupQueryAlter->doAlter() (Line: 143)
Drupal\group\QueryAccess\QueryAlterBase->alter() (Line: 333)
group_query_entity_query_alter() (Line: 552)
Drupal\Core\Extension\ModuleHandler->alter() (Line: 494)
Drupal\Core\Database\Query\Select->preExecute() (Line: 519)
Drupal\Core\Database\Query\Select->execute() (Line: 157)
Drupal\pgsql\Driver\Database\pgsql\Select->execute() (Line: 272)
Drupal\Core\Entity\Query\Sql\Query->result() (Line: 85)
Drupal\Core\Entity\Query\Sql\Query->execute() (Line: 391)
Drupal\Core\Entity\Plugin\EntityReferenceSelection\DefaultSelection->validateReferenceableEntities() (Line: 133)
Drupal\Core\Entity\Plugin\Validation\Constraint\ValidReferenceConstraintValidator->validate() (Line: 202)
Drupal\Core\TypedData\Validation\RecursiveContextualValidator->validateConstraints() (Line: 154)
Drupal\Core\TypedData\Validation\RecursiveContextualValidator->validateNode() (Line: 164)
Drupal\Core\TypedData\Validation\RecursiveContextualValidator->validateNode() (Line: 106)
Drupal\Core\TypedData\Validation\RecursiveContextualValidator->validate() (Line: 93)
Drupal\Core\TypedData\Validation\RecursiveValidator->validate() (Line: 132)
Drupal\Core\TypedData\TypedData->validate() (Line: 518)
Drupal\Core\Entity\ContentEntityBase->validate() (Line: 25)
Drupal\group\Entity\GroupMembership->preSave() (Line: 528)
Drupal\Core\Entity\EntityStorageBase->doPreSave() (Line: 753)
Drupal\Core\Entity\ContentEntityStorageBase->doPreSave() (Line: 483)
Drupal\Core\Entity\EntityStorageBase->save() (Line: 806)
Drupal\Core\Entity\Sql\SqlContentEntityStorage->save() (Line: 354)
Drupal\Core\Entity\EntityBase->save() (Line: 166)
Drupal\ginvite\EventSubscriber\GinviteSubscriber->autoAcceptGroupInvitation()
call_user_func() (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch() (Line: 327)
_ginvite_handle_new_user_registration_or_update() (Line: 274)
ginvite_user_insert()
call_user_func_array() (Line: 416)
Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}() (Line: 395)
Drupal\Core\Extension\ModuleHandler->invokeAllWith() (Line: 423)
Drupal\Core\Extension\ModuleHandler->invokeAll() (Line: 215)
Drupal\Core\Entity\EntityStorageBase->invokeHook() (Line: 900)
Drupal\Core\Entity\ContentEntityStorageBase->invokeHook() (Line: 564)
Drupal\Core\Entity\EntityStorageBase->doPostSave() (Line: 781)
Drupal\Core\Entity\ContentEntityStorageBase->doPostSave() (Line: 489)
Drupal\Core\Entity\EntityStorageBase->save() (Line: 806)
Drupal\Core\Entity\Sql\SqlContentEntityStorage->save() (Line: 354)
Drupal\Core\Entity\EntityBase->save() (Line: 100)
Drupal\user\RegisterForm->save()
call_user_func_array() (Line: 129)
Drupal\Core\Form\FormSubmitter->executeSubmitHandlers() (Line: 67)
Drupal\Core\Form\FormSubmitter->doSubmitForm() (Line: 597)
Drupal\Core\Form\FormBuilder->processForm() (Line: 144)
Drupal\autosave_form\Form\AutosaveFormBuilder->processForm() (Line: 326)
Drupal\Core\Form\FormBuilder->buildForm() (Line: 97)
Drupal\autosave_form\Form\AutosaveFormBuilder->buildForm() (Line: 73)
Drupal\Core\Controller\FormController->getContentResult()
call_user_func_array() (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 638)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext() (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 181)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 53)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle() (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 741)
Drupal\Core\DrupalKernel->handle() (Line: 19)