It's hard to explain
The hex is moving slightly in the wheel - this movement is probably worse on some wheels - and certainly worse on more worn wheels.
Under power the front right wheel might rotate back slightly (relative to the axle) and because the HB nut is securely tightened to the wheel any movement of the wheel effects the nut.
So..... the nut loosens slightly - which allows the wheel maybe to move a little - which loosens the nut, which allows the whe..... well, you get the idea.
So from nowhere the wheel can spin off really quickly!
The left hand wheel will tighten up under acceleration, so that's no problem.
This is really evident on high grip and BAD wheels. That's not to say the original 501X wheels are BAD - but they aren't amazing. The new DB01 wheels look virtually identical but have a much tighter hex - and so far I've not had this problem.
Once your wheel has come off it will always come off with these nuts. They hold things so stongly but are only as good as the wheels they attach.