Offset current in Gas Gauge calibration

I am dealing with a peculiar problem using the bq20z90 gas gauge chip.  My battery pack is a 4s3p connection of 18650 Li-Ion cells which have been set up using the default TI .senc file and a .gg file very close to the TI default file.  The problem is that after calibrating the pack, I get a zero offset current in the SBS screen, but upon connecting the pack to a power supply (current-limited) to charge the pack, the pack takes on an offset of between 30 and 70 mA. This offset remains until the pack is subjected to any amount of discharge current, at which time the offset goes away. Additionally, the CB (cell balancing) flag comes on when charging and goes off when the discharge starts.  This is happening on several modules so I don't think it is a cell-specific issue. I have consulted with TI Applications Engineering, and they seem to be at a loss as to what is going on.  The ciscuit is basically a copy of the Eval Module circuit with the 2nd level voltage shutdown cut out.  Any ideas out there?