Having a similar issue in Maya LT 2020. UV's keep on going back to a previous state, even if saved in different named files. Only one UV set, in this case one named Diffuse1, the one coming from Zbrush. The fix for me was to just create a new UV set, and then the UV's go to where thay should be. As a precautionary extra…
I had the same problem. UVs randomly disappearing. Somehow some of my geo was given a second UV set (which had the correct uvs) and left the original one blank and active. My guess is that because the default uv set wasn't named map1 this may have caused the bug. So I copied the correct uvs from the bad set to the default…
Now this is getting bizarre. I used the UV set editor to successfully paste the UVs from a good imported object to its corrupted counterpart. The corrupted object has UVs that can be seen in the UV texture editor but no plugged maps are displayed!
never seen the bug before, but have you tried copying the UVs to a new UV set and using that one? then maybe copy it back to map1? I've been having some UV issues exporting from maya 2014 to FBX2013 into UE4. The lightmaps get mixed up with map1 sometimes, so copy pasting UVs sometimes fixes the problem in that particular…