Couple of other things to try
Assign a new material to it. Sounds weird but I've seen this work before.
Export it out of the scene and reimport it into a new one. If you want to upload the scene I'd be happy to tell you if it does the same to me in Maya 2020
All the best
David
From a readers' Q and A column in TV GUIDE: "If we get involved in a nuclear war, would the electromagnetic pulses from exploding bombs damage my videotapes?"