I have fixed it up and sorted it today, i added more spacers into the gearbox, this mean the torque limiter can be set at a higher level.

I have done some testing (with the axe module out of the robot so i can change the limiter easily) I found a good torque amount, but I found that all the screws loosened on the gearbox over time, which meant the torque limiter loosened. Im unsure how to stop this, would lock-tight work on this plastic? for the 4 motor ones I could probably drill them though and bolt them, but would make it hard work and awkward to undo. so probably not a good idea. But do you think lock tight would work?