In a working workflow, I added a reference to an AD user and then deployed again. The reference did not capture what I needed. Then, I opened the workflow to review. Nothing wrong so I tried to re- deploy it again, but this time failed with the error:

"One of the properties in Activity vactivity] located in event vevent] is pointing to an external reference that does not exists."

I deleted the reference, re-deployed and success, but then again, I re-create the reference, deployed successfully but when reopening the workflow, the error message is back (figure is attached).

Thank you!