Firmware bug in K-5 IIs
..or indeed on any of the many connections between the cells and the camera. Also, there could well be a semiconductor fuse in the output of the grip that is just tripping when the camera goes into peak load. That would be my favourite guess. A firmware problem would be well down my list.
If the EXIF contains the voltages then that would be a very good place to start.
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from Abstract Architecture
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