if the bms it's self has not taken any damage, then there might be some loose connectors or damaged sensors causing the issues as well. you also could have jarred something loose in places you can't see either, like in the battery compartment on some bus work, voltage sensors or something like that. This doesn't mean that it's fine, you could have busted stuff on the bms board, just that it could be getting bad inputs from other places causing your problems. Given it seemed fine then the problems creeped in, sounds like something is loose, and now giving you grief over it. There could also be some pinched wires too as everything got slammed in the crash. BMS' have a lot of small signal wires that arent always routed in the best way, and any hard shocks can pinch them, cut them, or fray them. if it's looking at individual battery volts, now were talking only a few volts, so a slightly loose or even a bit off being full seated connector can absolutely cause you grief.
loose buswork can cause issues that will only appear after some use, as charge / discharge don't happen properly due to voltage swings across the loose connections now start causing short charge cycles, improper soc indictions etc due to them.
do you have some sort of factory reset option you could try, like a total reboot or default setting, see if that might help? Set it to day 1 settings so you are starting with a clean slate, then anything creeping in, you know is current.
aaron