I have Shimano XTR M965 shifters and hydraulic brakes on my MTB. The rear brake hose and caliper still seem to have air in them although I rebleeded the brake several times in trying to get all the air out. The rear brake does not squeeze very tight. Every time I squeeze the lever hard to brake while riding, it would shift from the current cog to larger one(s).
Is this normal? What should I try to fix the problem?