Symmetra multiple simultaneous SYBT5 battery module failures

[DrewP]

Thanks to this thread I've been repairing my SYBT5 battery modules. I recently learned that a bad module can cause other modules to fail even though their batteries are all ok. My Symmetra has 4 battery modules. One day it said that 3 of them had failed and the 4th was failing with errors such as 'low capacity' etc. I checked the EEPROMS and found that the one from the failing module had been corrupted. I was unable to reprogram it, and when I installed a new EEPROM it became corrupted too. This made me think that the module's microcontroller was damaged. I installed a control board from a spare module and reprogrammed all 4 EEPROMs. After that all modules were ok.