It doesnt revert to OE software, it reverts to OE equivalent power output in terms of boost request due to the fact that Revo offer switchable mapping and the way in which the selected map is held in the ECU memory
If you've been lucky and the ECU has managed to retain its memory (residual charge etc.) then it saves you a trip. The difference between Revo stock and Revo Stage 1 on the GTI is night & day - the car feels broken, flat and lifeless going from Stage 1 to their equivalent OE output
Some more info would help, such as when you had the Revo software done, when you started to experience issues, whether the issues started at the same time you had the battery off etc.