Main breaker tripping, dead CIM

[Oblarg]

After having nearly no problems with our drive for all of Greater DC, our robot started tripping our main breaker in matches today (problem arose as the day went on, in our last two matches we tripped the breaker about halfway through). Upon testing, we discovered a few things:

1) From a cold start, it takes ~20 seconds of pushing against a wall to trip our main breaker.
2) The wires going to the breaker from the battery heated up noticeably during this time.
3) One of our CIMs was badly damaged; the front ring was able to turn independently from the body of the CIM.

We replaced the CIM (and for good measure replaced the breaker), but are wondering why the problem cropped up so suddenly and if the dead CIM could have been exacerbating it. Any thoughts? We have not been able to test since replacing the parts, unfortunately.

We're running a 6-CIM modified KOP drive with HiGrip wheels geared for 14 fps.