Just when you thought only DPSS lasers danced between screwed-up TEM modes...
The diode is from an unidentified Samsung DVD burner (presumably 16x judging from manufacture date). The diode was tested working beforehand and ran just fine. Being driven at 150mA from an O-Like driver, for roughly 80mW out when metered.
I don't know why it suddenly decided to start mode-hopping, and it's also run stable since. Racked up a few hours on it last night, was perfectly stable whole way through.
Normally when diodes mode-hop they don't go into higher-order rectangular transverse modes, so I thought I'd video it and share.