When undoing, it's common for random, undesired changes to occur. The ATV in the screenshot iz not meant to have parts hanging out the front; it looked correct before I pressed undo. This is not the only undo to break it; I reloaded the ATV after undo broke it in a different way. [More to follow]
More info I didn't want to type on mobile:
The vehicle is SimpleATV minus the exhausts, plus some panels and blocks, with the tail lights moved, with the root part re-shaped and of course recolored. (I don't think I made any other permanent changes, though I changed some things and changed them back a week or 2 ago.) Symmetry is clearly broken, the miss-fitted parts in the screenshot were symmetrical.