Edit: is it possible that the odd forces involved with the chain tension suddenly snapping under load did something odd to the BB? There does seem to be more flex when testing the pedals than normal.
I'm checking the stays for damage as well though this seems unlikely.
Unfortunately the cage has possibly been bent. I'm getting ghost shifts and a rattling feeling similar to FD chain rub only when pedaling.
The cage is OK with the eyeball test, and seems to function alright when backpedaling (and oddly enough, when hand cranking with the bike in a stand) but seems to have a minor amount of play (roll) to the cage- without a known good derailleur I don't know how normal this is. It's also possible it just doesn't like the 9 speed chain.
LBS time, then, as I think this is beyond my ability to diagnose.
Last edited by sheddle; 08-25-20 at 09:25 AM.