I have a Sunsynk 5kw inverter with a Pylontech US2000C master battery with three Pylontech US2000B batteries. This December after the system had been running for two years the master US2000C failed (it was swollen on the structure) while the other three batteries remained in perfect condition. I am currently running on the remainder without any alarms or problems. I have sent the battery in for a technical report but I would like to know what could be the root cause of the problem.