Possibly not too useful, but I did have a printer that had a firmware bug that would screw up the PID if the X and Y axis steps/mm were adjusted.

This may be similar, where the wrong variables are being changed. Do you know what firmware it's based on, and is it running a custom interface over the top? E.g., is it Marlin underneath, with a touchscreen and a custom interface firmware on top? If so, can you connect via computer and find out what the real values are using something like Pronterface?