I can't speak for the Q7 but on the old allroads this issue can be caused by leaking airbags. Also alot of times the wire for the sensor can stretch besides breaking from even normal driving, or the plug will just become unseated, also causing the problem on the allroads. Very good possibility that could be the case. I would check the sensor wiring and plug first being it could be the cheapest fix. Another thing to consider is a faulty module.
Hope this helps.