InvalidArgumentException: Field shipments is unknown.

Problem/Motivation

Error while proceeding checkout: InvalidArgumentException: Field shipments is unknown.

Steps to reproduce

Create Inpost shipping method (followed module's readme.md). Add products to the cart. Proceed to checkout as a guest. The following error occurres:

InvalidArgumentException: Field shipments is unknown. in Drupal\Core\Entity\ContentEntityBase->getTranslatedField() (line 616 of .../web/core/lib/Drupal/Core/Entity/ContentEntityBase.php).

#0.../web/core/lib/Drupal/Core/Entity/ContentEntityBase.php(597): Drupal\Core\Entity\ContentEntityBase->getTranslatedField('shipments', 'x-default')
#1 .../web/modules/custom/commerce_inpost/src/Plugin/Commerce/CheckoutPane/InPostPane.php(469): Drupal\Core\Entity\ContentEntityBase->get('shipments')
#2 .../web/modules/custom/commerce_inpost/src/Plugin/Commerce/CheckoutPane/InPostPane.php(135): Drupal\commerce_inpost\Plugin\Commerce\CheckoutPane\InPostPane->getShippingProfile()
#3 .../web/modules/contrib/commerce/modules/checkout/src/Plugin/Commerce/CheckoutFlow/CheckoutFlowWithPanesBase.php(546): Drupal\commerce_inpost\Plugin\Commerce\CheckoutPane\InPostPane->buildPaneForm(Array, Object(Drupal\Core\Form\FormState), Array)
#4 [internal function]: Drupal\commerce_checkout\Plugin\Commerce\CheckoutFlow\CheckoutFlowWithPanesBase->buildForm(Array, Object(Drupal\Core\Form\FormState), 'order_informati...')