Symptoms

After rolling out Appit update 4, we noticed that their workflows does not start using SharePoint remote event receivers any longer. In addition to that, you get an "Object Ref" error when starting the workflow manually.
 

Diagnoses

This was a bug that was introduced in Appit update 4.
 

Resolution

We applied the fix to the client's production environment and it resolved the issue. (We rolled out the "global update" on 08/25/2016.)