Hey MacFevre,
I have experienced exactly the same problem. In fact, I'm currently experiencing that problem again, but since I'm flying BMS Falcon these days and have my throttles linked, it's not a problem.
When I first noticed the problem I contacted Thrustmaster support, but they just replied with the default calibration crap ... which of course did nothing to resolve the problem.
I did open up my throttle back then and applied some pressure on a contact board (PCB I believe) and then the right throttle responded properly again. Sorry I can't give you more details as it's been more than a year ago since I did this.
In either case: I have my money on a hardware problem related to a bad contact somewhere.
Br,
Mud