Content translation: Site breaks on adding content translations

Problem/Motivation

When adding Icelandic (and other) language translations, the site breaks and displays the following error. There are also different paragraph blocks on the page, and all fields inside paragraphs have "Users may translate this field" enabled.
here is the stack tree.

TypeError: count(): Argument #1 ($value) must be of type Countable|array, null given in count() (line 213 of /var/www/project/qa4/application/docroot/core/modules/content_translation/src/FieldTranslationSynchronizer.php)
#0 /var/www/project/qa4/application/docroot/core/modules/content_translation/src/FieldTranslationSynchronizer.php(213): count(NULL)
#1 /var/www/project/qa4/application/docroot/core/modules/content_translation/src/FieldTranslationSynchronizer.php(171): Drupal\content_translation\FieldTranslationSynchronizer->synchronizeItems(Array, Array, 'is', Array, Array)
#2 /var/www/project/qa4/application/docroot/core/modules/content_translation/content_translation.module(531): Drupal\content_translation\FieldTranslationSynchronizer->synchronizeFields(Object(Drupal\paragraphs\Entity\Paragraph), 'is', NULL)
#3 [internal function]: content_translation_entity_presave(Object(Drupal\paragraphs\Entity\Paragraph))
#4 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Extension/ModuleHandler.php(426): call_user_func_array(Object(Closure), Array)
#5 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Extension/ModuleHandler.php(405): Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}(Object(Closure), 'content_transla...')
#6 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Extension/ModuleHandler.php(433): Drupal\Core\Extension\ModuleHandler->invokeAllWith('entity_presave', Object(Closure))
#7 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/EntityStorageBase.php(251): Drupal\Core\Extension\ModuleHandler->invokeAll('entity_presave', Array)
#8 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php(903): Drupal\Core\Entity\EntityStorageBase->invokeHook('presave', Object(Drupal\paragraphs\Entity\Paragraph))
#9 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/EntityStorageBase.php(563): Drupal\Core\Entity\ContentEntityStorageBase->invokeHook('presave', Object(Drupal\paragraphs\Entity\Paragraph))
#10 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php(756): Drupal\Core\Entity\EntityStorageBase->doPreSave(Object(Drupal\paragraphs\Entity\Paragraph))
#11 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/EntityStorageBase.php(517): Drupal\Core\Entity\ContentEntityStorageBase->doPreSave(Object(Drupal\paragraphs\Entity\Paragraph))
#12 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php(802): Drupal\Core\Entity\EntityStorageBase->save(Object(Drupal\paragraphs\Entity\Paragraph))
#13 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/EntityBase.php(339): Drupal\Core\Entity\Sql\SqlContentEntityStorage->save(Object(Drupal\paragraphs\Entity\Paragraph))
#14 /var/www/project/qa4/application/docroot/modules/contrib/entity_reference_revisions/src/Plugin/Field/FieldType/EntityReferenceRevisionsItem.php(310): Drupal\Core\Entity\EntityBase->save()
#15 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Field/FieldItemList.php(233): Drupal\entity_reference_revisions\Plugin\Field\FieldType\EntityReferenceRevisionsItem->preSave()
#16 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Field/FieldItemList.php(191): Drupal\Core\Field\FieldItemList->delegateMethod('preSave')
#17 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php(941): Drupal\Core\Field\FieldItemList->preSave()
#18 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php(891): Drupal\Core\Entity\ContentEntityStorageBase->invokeFieldMethod('preSave', Object(Drupal\node\Entity\Node))
#19 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/EntityStorageBase.php(563): Drupal\Core\Entity\ContentEntityStorageBase->invokeHook('presave', Object(Drupal\node\Entity\Node))
#20 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php(756): Drupal\Core\Entity\EntityStorageBase->doPreSave(Object(Drupal\node\Entity\Node))
#21 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/EntityStorageBase.php(517): Drupal\Core\Entity\ContentEntityStorageBase->doPreSave(Object(Drupal\node\Entity\Node))
#22 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php(802): Drupal\Core\Entity\EntityStorageBase->save(Object(Drupal\node\Entity\Node))
#23 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/EntityBase.php(339): Drupal\Core\Entity\Sql\SqlContentEntityStorage->save(Object(Drupal\node\Entity\Node))
#24 /var/www/project/qa4/application/docroot/core/modules/node/src/NodeForm.php(270): Drupal\Core\Entity\EntityBase->save()
#25 [internal function]: Drupal\node\NodeForm->save(Array, Object(Drupal\Core\Form\FormState))
#26 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Form/FormSubmitter.php(114): call_user_func_array(Array, Array)
#27 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Form/FormSubmitter.php(52): Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object(Drupal\Core\Form\FormState))
#28 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Form/FormBuilder.php(592): Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object(Drupal\Core\Form\FormState))
#29 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Form/FormBuilder.php(320): Drupal\Core\Form\FormBuilder->processForm('node_localized_...', Array, Object(Drupal\Core\Form\FormState))
#30 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Entity/EntityFormBuilder.php(48): Drupal\Core\Form\FormBuilder->buildForm(Object(Drupal\node\NodeForm), Object(Drupal\Core\Form\FormState))
#31 /var/www/project/qa4/application/docroot/core/modules/content_translation/src/Controller/ContentTranslationController.php(394): Drupal\Core\Entity\EntityFormBuilder->getForm(Object(Drupal\node\Entity\Node), 'default', Array)
#32 [internal function]: Drupal\content_translation\Controller\ContentTranslationController->add(Object(Drupal\Core\Language\Language), Object(Drupal\Core\Language\Language), Object(Drupal\Core\Routing\RouteMatch), 'node')
#33 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array)
#34 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/Render/Renderer.php(564): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#35 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#36 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)
#37 /var/www/project/qa4/application/vendor/symfony/http-kernel/HttpKernel.php(158): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#38 /var/www/project/qa4/application/vendor/symfony/http-kernel/HttpKernel.php(80): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#39 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/StackMiddleware/Session.php(58): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#40 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#41 /var/www/project/qa4/application/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#42 /var/www/project/qa4/application/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#43 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#44 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#45 /var/www/project/qa4/application/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#46 /var/www/project/qa4/application/docroot/core/lib/Drupal/Core/DrupalKernel.php(709): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#47 /var/www/project/qa4/application/docroot/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#48 {main}

Steps to reproduce

Proposed resolution

NA

Remaining tasks

User interface changes

NA

API changes

Data model changes

Release notes snippet