Symetra px battery burn

[BillP]

Hi,

I had a bad experience with an Apc symmetra px160 kw. When replacing my batteries 9 month ago,  the Apc technician realized that a BMB card was defective in one of my battert Frame. He still decided to connect the batteries in the lower part of the battery cabinet since only one BMB was defective. As you know there is 2 BMB in each battery frame.  He also disconnected the XR communication card so that the ups does not display an alarm.

Last night: Disaster! A battery module burned completely causing a fire. I remind you that the batteries were almost new as we installed it 9 month ago.

Knowing that there is two BMB inside the battery frame and the batteries were installed in the bottom of the battery frame and the bottom BMB was good. Only the upper BMB was faulty. I Remind you the Apc technical guy disconected  the XR communication to avoid an batteries faulty alarm. So this can cause a battery module to burn? 

OR the problem is more like a manufacturing defect in the battery module ?

Or the problem is the battery frame itself which is 7 years old ...?