Twice now I've had an odd issue which I think is the BMS.
I've got a 16s pack using ETC 277ah cells and am about 100 cycles in, the pack was top balanced for a good week before it went in and i have balancing on.
This morning, with the heater on and the kettle boiling, the BMS logged a low voltage alert on a particular cell and disconnected the loads. It was pulling about 100amps, but the battery was about 70% full so the voltage sag still had the pack voltage above 51v as a whole, just 2.9v on one particular cell. Temp monitoring said about 15deg on the pack.
I went and rebooted the inverter (no solar at this time, it was early) and then loaded it all back up and grabbed the multimeter to test the cell under load and didn't see anything below 3v on the multimeter, but more like 3.1v as the BMS is reporting low 2.9v on that one cell. Using a fluke 325 which only has 1decimal place so it could be rounding up and could also not be updating fast enough for me to see real voltages.
That said, I had this same issue last week, but on a different cell and you'd think if I had a bad cell it would be consistent.
I've also noticed, that each time I reboot the BMS, the cell balance wire lead resistance values are increasing. Is there an underlying issue here? All connections look good/no corrosion etc.