I'd hoped to attach a pump below the bottle cage, but the one screw holding the cage won't come out because the rivnut in the frame somehow unwelded itself from the aluminium while I tried to loosen it. Of course it can't be tightened either, so now it rattles too. The cage is in the way, so I can't grip the rivnut to try and turn the screw out. I'm a bit worried about cutting/drilling it off in case it drops inside the frame. Has anybody tried this and have any advice? Thanks.