hmm is it possible that as a result of the touches the wires and/or sensing pads move, thus affecting baseline capacitance?
I would set the sensor to RAW mode and look at what happen to the raw readings when touching / releasing. Use the general-settings or craft-settings examples for this and see if parameter tweaking helps you isolate the issue.
A side note: if your needs change while the application is running, you could e.g.: set lower prescaler to detect proximity and then switch to higher prescaler once the touch starts, to get more details of the touch itself (if relevant). These settings are global for all the sensor pads, so it may be a bit complicated to switch back and forth if each pad is doing a different thing. The Rev C firmware makes it a bit easier in that unused pads can be excluded from scanning and there is more granular control over how to trigger a scan.
