Can't save new nodes following beta2 upgrade (Assertion Error)

Note: I am selecting version 8.x-2.0-beta1 but this problem is specific to 8.x-2.0-beta2 (it isn't an option in the select list).

We were using the alpha1 release and everything was working great (thank you!).

But we upgraded to 8.x-2.0-beta2 yesterday (and I ran the database updates successfully) and now when I try to create a new node that has a date_recur field, I get WSOD with the Assertion Error below.

Interestingly, problem does not occur when editing an existing node - just when creating a new one.

The website encountered an unexpected error. Please try again later.
AssertionError: assert(!empty($defaultDateTimeZone)) in assert() (line 173 of modules/contrib/date_recur/src/Plugin/Field/FieldType/DateRecurFieldItemList.php).
assert(, 'assert(!empty($defaultDateTimeZone))') (Line: 173)
Drupal\date_recur\Plugin\Field\FieldType\DateRecurFieldItemList::processDefaultValue(Array, Object, Object) (Line: 405)
Drupal\Core\Field\FieldConfigBase->getDefaultValue(Object) (Line: 169)
Drupal\Core\Field\FieldItemList->applyDefaultValue() (Line: 149)
Drupal\Core\Entity\ContentEntityStorageBase->initFieldValues(Object, Array) (Line: 91)
Drupal\Core\Entity\ContentEntityStorageBase->doCreate(Array) (Line: 221)
Drupal\Core\Entity\EntityStorageBase->create(Array) (Line: 110)
Drupal\node\Controller\NodeController->add(Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 582)
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}() (Line: 151)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
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: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 693)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)