In reply to J1234:
Here are things that will help the binding issue:
1. Try a rounder carabiner
2. Try low-friction mode.
3. Try using two carabiners, but with the second one NOT clipped to the belay loop.
Extending the rappel is the best and safest way to employ an autoblock backup. And it is also a good way to get more control from a device that isn't quite grabby enough, because the extended device allows for the brake strand to be held more nearly vertical and so more friction is obtained. However, if the problem is already too much friction, then extending the rappel is only going to make that more pronounced, although one of items 1--3 will still alleviate it.