Sometimes to random points in my unwrapping process. Unwrapped a bunch of different objects only to go back to the first ones I unwrapped and found half of them to randomly be reverted. So, I just lost about 3 hours of work from this bug. It's a really painful bug and I'm really surpirsed it hasn't gained more traction. The critical issue is that when we make edits to uv1, we lose our uv2's, they are completely reset. We have our texture unwrap on uv1 and then a second unwrap above on uv2 for lightmaps.
Our key workflow that will stop us is related to having 2 uvw channels for lightmaps. (In my gif example, I had a chamfer turned off underneath - this might be why my uvw reset on copying, where it didn't in the webinar.) Do this is any version prior to 2021 and this will work fine. For example, stack a push mod, then unwrap ontop, then edit your push value by an amount and note that the unwrap above is reset. As I explained in greater detail in my bug report, it appears related to editing modifers under the uvw unwrap, even when no topology change has been made. We're about to start work on our next game, and its unlikely we can move our team to 2021 with this issue present as one of our key workflows is fundamentally broken.
