Actually I think it was the NVR, somehow. I deleted from the NVR and defaulted the camera. I then created a simple user with limited access to the camera. added the camera with that user account (not admin) and have never had the problem again.
DS-2DF8236I5X-AELW
Upgraded from V5.5.8 build 180917 to V5.6.0 build 190130.
When I change WDR to ON, it immediately shows ON and the WDR setting then goes back to OFF. Says saved ok? Tried from Camera menu and fails the same way.
Any Ideas?