I'm guessing not tightened correctly.
It's a castle nut, the type with the top pinched a bit to be like a locking one.
Admittedly, it IS on a slap shifter. So that could have helped it go bad. But I wouldn't have thought this soon, since a don't slap shift unless I'm doing 1/4 mi, or 0-100 runs.
Off which I haven't really done many this year.
But... As stated , the stereo has caused a few issues too lol.
Swapped a bunch of nuts for brackets and suck like exhaust, etc. to Nyloc style. Because a few things have come free.
Between that, and RTV as loctite, think I found most of the places it was happening.