Sounds more like the tension is set too high / tight. When I was persuaded to go clipless with Shimano M515s, the LBS manny loosened the tension off to a minimal setting ' 'til I got used to them '. I've never tightened them since, as the particular setting works for me insofar that on the odd ocasion I've involuntarily come off my bike, the spds have always unclipped without any concious effort from me. But in everyday cycling, they hold in place just fine for me.