BMS failures
There are several way to check whether BMS is failures:
1. appearance inspection: Observe the MOSFETs, If there any  explosion or got fire on components.
2. Voltage measure : Measure the voltage between B- and the total  positive terminal and between P- and the total positive terminal. If the voltages are the same, the BMS  is good. If there is a  voltage difference, the BMS may be failures.
3. Resistance measurement: Measure the resistance between B- and P-. If the resistance is 0, the bms voltage  is normal. If there is no conduction, it might indicate that the MOSFETs are not working correctly or there is an issue with BMS.

Different BMS manufacturers may have different circuit designs and testing methods,  If the manufacturer’s information is not available, one way to check if the BMS has a ploblem is by replacing it.
When you find there is problem with  BMS, We generally recommend to replace it rather than try to repair it. because  one component is damaged, it may lead to a chain reaction affecting other components’ performance
The damage of BMS is caused by mismatches in charging voltage and current.
When you prepare repairs a battery pack , You must need to know the  charger model, voltage, current, and other parameters of charger to ensure compatibility