PluginCollectionItemBase should unserialize plugin configuration

Same issue, cannot execute Cron because of this.
Cannot uninstall module because I have to run cron to uninstall Payment Form Field module which needs cron to run before I can uninstall it because it has fields pending deletion.

The website encountered an unexpected error. Please try again later.
TypeError: Argument 1 passed to Drupal\plugin\Plugin\Field\FieldType\PluginCollectionItemBase::setContainedPluginConfiguration() must be of the type array, string given, called in /var/www/drupalvm/eura/webroot/modules/contrib/plugin/src/Plugin/Field/FieldType/PluginCollectionItemBase.php on line 202 in Drupal\plugin\Plugin\Field\FieldType\PluginCollectionItemBase->setContainedPluginConfiguration() (line 108 of modules/contrib/plugin/src/Plugin/Field/FieldType/PluginCollectionItemBase.php).
Drupal\plugin\Plugin\Field\FieldType\PluginCollectionItemBase->setContainedPluginConfiguration('a:5:{s:4:"name";s:13:"payment_basic";s:8:"quantity";s:1:"1";s:6:"amount";s:2:"50";s:13:"currency_code";s:3:"EUR";s:11:"description";s:19:"kjh hsqkdhsqhdjkqsh";}') (Line: 202)
Drupal\plugin\Plugin\Field\FieldType\PluginCollectionItemBase->setValue(Array, ) (Line: 195)
Drupal\Core\TypedData\TypedDataManager->getPropertyInstance(Object, 0, Array) (Line: 82)
Drupal\Core\Field\FieldTypePluginManager->createFieldItem(Object, 0, Array) (Line: 40)
Drupal\Core\Field\FieldItemList->createItem(0, Array) (Line: 66)
Drupal\Core\TypedData\Plugin\DataType\ItemList->setValue(Array, ) (Line: 118)
Drupal\Core\Field\FieldItemList->setValue(Array, ) (Line: 106)
Drupal\Core\TypedData\TypedDataManager->create(Object, Array, 'field_pay', Object) (Line: 1579)
Drupal\Core\Entity\Sql\SqlContentEntityStorage->readFieldItemsToPurge(Object, 50) (Line: 175)
Drupal\Core\Entity\ContentEntityStorageBase->purgeFieldData(Object, 50) (Line: 96)
field_purge_batch(50) (Line: 167)
field_cron()
call_user_func_array('field_cron', Array) (Line: 391)
Drupal\Core\Extension\ModuleHandler->invoke('field', 'cron') (Line: 223)
Drupal\Core\Cron->invokeCronHandlers() (Line: 122)
Drupal\Core\Cron->run() (Line: 75)
Drupal\Core\ProxyClass\Cron->run() (Line: 171)
Drupal\admin_toolbar_tools\Controller\ToolbarController->runCron()
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 574)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
call_user_func_array(Object, Array) (Line: 144)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 64)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 656)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Thanks, that really helped!
Searched for: s:4:"name";s:13:"payment_basic";
As mentioned in my error on running cron.

Found two database fields and removed them manually.
Issue is solved now!

On line 108 of Drupal\plugin\Plugin\Field\FieldType\PluginCollectionItemBase.php this is the line that produces the Exception Error..and I think what it says is that 'plugin_configuration' should be a key in the $configuration array. Is there a better way to solve this.

Seems like a serious problem.

Fixing priority; needs more information on reliably replicating this.

I had the same issue applied this patch to fix it.

@Ujin can you provide steps to reliably reproduce the problem?

@jonathanshaw I have Drupal 8.7.1 and next contrib modules:
entity_reference_quantity
entity_reference_revisions
field_formatter_class
field_group
field_states_ui
libraries
page_load_progress
paragraphs
parallax_bg
pathauto
payment
payment_offsite_api
paypal_payment
plugin
And on every page I had in the bottom message about fatal error. I think will need to try with fresh installation in order to reproduce the issue.

I had a similar problem because I didn't delete payment data before deleting the actual fields. I was able to resolve by deleting the "deleted" data/revision content and tables directly from the database.

Steps to reproduce:

* Add plugin field to any content type
* Add a node, filling plugin information
* Delete the new field
* Run cron to purge the new field
* See the error in error log

@ stone_d
thank you !!

Reroll against the latest version 2.9

This issue still occurs with the current version of the module (version 2.11). It seems to me it would be good to get the patch committed, especially since this issue has been around for 6 years now.

The current patch in #16 applies cleanly to version 2.11 of the module, the code looks good to me.

Is a test needed to get this committed?