Have a look at this thread: Random Pylontech Swollen Batteries on 900-1200 Cycles
My us3000c batteries exhibiting the same behavior along with alarms and errors from the inverter.
My 1st battery was replaced, I just need to go collect it (was emailed today about it). My 2nd one I also need to RMA now.
As soon as I removed the problematic batteries from my stack, the others showed charging normally to 100%.
Anyways, I think you also have a faulty battery.