9 – Database Serialization Error when editing Paragraphs after upgrading to D9

I’m upgrading my sites to Drupal 9. I’m only seeing one issue after the update when clicking “Edit” on a Paragraph on one of my pages:

An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /node/691/edit?ajax_form=1
StatusText: error
ResponseText: The website encountered an unexpected error. Please try again later.LogicException: The database connection is not serializable. This probably means you are serializing an object that has an indirect reference to the database connection. Adjust your code so that is not necessary. Alternatively, look at DependencySerializationTrait as a temporary solution. in DrupalCoreDatabaseConnection->__sleep() (line 1826 of core/lib/Drupal/Core/Database/Connection.php). serialize(Array) (Line: 14)
DrupalComponentSerializationPhpSerialize::encode(Array) (Line: 111)
DrupalCoreKeyValueStoreDatabaseStorageExpirable->doSetWithExpire('form-GeirjRgkOxybCxOKd8UyfCEMS1nxWYErh2e5RxEI8Z0', Array, 21600) (Line: 122)
DrupalCoreKeyValueStoreDatabaseStorageExpirable->setWithExpire('form-GeirjRgkOxybCxOKd8UyfCEMS1nxWYErh2e5RxEI8Z0', Array, 21600) (Line: 193)
DrupalCoreFormFormCache->setCache('form-GeirjRgkOxybCxOKd8UyfCEMS1nxWYErh2e5RxEI8Z0', Array, Object) (Line: 459)
DrupalCoreFormFormBuilder->setCache('form-GeirjRgkOxybCxOKd8UyfCEMS1nxWYErh2e5RxEI8Z0', Array, Object) (Line: 437)
DrupalCoreFormFormBuilder->rebuildForm('node_landing_page_edit_form', Object, Array) (Line: 629)
DrupalCoreFormFormBuilder->processForm('node_landing_page_edit_form', Array, Object) (Line: 321)
DrupalCoreFormFormBuilder->buildForm(Object, Object) (Line: 73)
DrupalCoreControllerFormController->getContentResult(Object, Object) (Line: 39)
Drupallayout_builderControllerLayoutBuilderHtmlEntityFormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
DrupalCoreEventSubscriberEarlyRenderingControllerWrapperSubscriber->DrupalCoreEventSubscriber{closure}() (Line: 573)
DrupalCoreRenderRenderer->executeInRenderContext(Object, Object) (Line: 124)
DrupalCoreEventSubscriberEarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
DrupalCoreEventSubscriberEarlyRenderingControllerWrapperSubscriber->DrupalCoreEventSubscriber{closure}() (Line: 158)
SymfonyComponentHttpKernelHttpKernel->handleRaw(Object, 1) (Line: 80)
SymfonyComponentHttpKernelHttpKernel->handle(Object, 1, 1) (Line: 57)
DrupalCoreStackMiddlewareSession->handle(Object, 1, 1) (Line: 47)
DrupalCoreStackMiddlewareKernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupalpage_cacheStackMiddlewarePageCache->pass(Object, 1, 1) (Line: 85)
Drupalpage_cacheStackMiddlewarePageCache->handle(Object, 1, 1) (Line: 91)
DrupalshieldShieldMiddleware->handle(Object, 1, 1) (Line: 47)
DrupalCoreStackMiddlewareReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
DrupalCoreStackMiddlewareNegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
StackStackedHttpKernel->handle(Object, 1, 1) (Line: 706)
DrupalCoreDrupalKernel->handle(Object) (Line: 19)

I’m at a loss as to where to look to solve this issue.

Where is this breaking?

Thank you!