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Allowed moderation states (Unpublished)
Archived
Draft
Needs Review
The allowed unpublished moderation states this content-type can be assigned.
Allowed moderation states (Published)
Published
The allowed published moderation states this content-type can be assigned.
Default moderation state
Draft
Select the moderation state for new content
[Save] Delete
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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: 


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