I have poly groups for a jacket. They are separated by UV tiles, Jacket main body, left arm, right arm.
When I was ready to export the different normal maps I use polygroups to hide all but one tile.
Then I use the Morph UV to lay it out flat, so that I can just check it once before the normal map export. But I accidentaly unhide the other tiles while in Morph UV mode. Then I unmorphed it back to the original shape, then morphed it back flat again, and KABOOM!!! verts explode everywhere. Cris-crossing the model and not returning to their proper places.
This is a sure fire way of making your model explode… BUT WHY!!! HOW DO YOU FIX!!!