OK, today I ran the TPU in test mode, and one of the axes of the joystick had a permanent deviation that was not possible to calibrate Do you think it is possible to use the TPU from a S4C M97 controller for testing?
EDIT:
Took the TPU in and opened it up, there was some corrosion on the small connector on the joystick, cleaned it with some alcohol, cut off the connector, cleaned it too and reterminated. Tested, and the robot moves I got a "joystick error, joystick disabled" message on the TPU display so there might still be some issues with this connector, but it was OK after a reboot. Thanks for the help guys, really appreciated