
The car is in mint condition and the front belts in the car work fine. The rears look to be in good condition but do not 'lock' when pulled out abruptly. Both rear seatbelts exhibit this behavior.
Conversely my girlfriend has a Corsa hatchback of the same year and the back belts lock instantly in the same scenario.
What could be wrong? The belt mechanism looks fine to the casual observer and I just can't imagine that both rear belts would have developed the exact same problem when the car is in such good condition.
If the answer is simply 'replace them', ideas on their cost from a wrecker?