Moderation and Workbench

I am tryng to configure Moderation for my site. Drupal 8.4.2
I installed the various (latest) Workbench and Moderation Modules and found it wasn’t fully configured.
In going through the helpful videos (Created for Drupal v7.x) I got to the stage where you enable moderation on the content type you are working with
While adding a moderation state for Posts:
I got to the screen:
Home/Administration/Structure/Content types/Post
Which has the following:
Enable moderation states.
Content of this type must transition through moderation states in order to be published.
Allowed moderation states (Unpublished)
Needs Review
The allowed unpublished moderation states this content-type can be assigned.
Allowed moderation states (Published)
The allowed published moderation states this content-type can be assigned.
Default moderation state
Select the moderation state for new content
[Save] Delete

I clicked on the “Save” Button
and this fatal error resulted:

Fatal error: Call to undefined method Drupalcontent_moderationEntityHandlerNodeModerationHandler::onBundleModerationConfigurationFormSubmit() in /home/MYSITE/dev/site/modules/workbench_moderation/src/Form/BundleModerationConfigurationForm.php on line 184

Any thoughts?

Drupal version: