*Dozens* of crashed UFOs.
Technology so advanced it can travel interstellar space, but when it gets here, it suddenly gives out and crashes with apparent regularity for there to be “dozens” of crashes - and not just the tech from one other advanced civlization - but at least 4 - all so advanced to travel interstellar/intergalactic space, but again, they get here, and it fails for all of them.
F-35s, a technology so advanced that they crash after flying 100 miles.