From what you've done it does seem like you've assembled the capacitor bank properly. So with a properly assembled package that repeatedly fails, this leads to only two other options, poor design or operation control. Both options require more information like a schematic, operational signal measurements and verification that the actual assembly is being used as the designer intended. In other words, a knowledgeable person on site to troubleshoot your repetitive failures.

Now if I was there, the first thing I would do would be to verify that the schematic agreed with the actual circuit assembled. Next I would measure the currents running through the circuit breaker and capacitor bank with a clamp on ammeter and oscilloscope. Then and only then might I have a suggestion which might be your cause of failure.