Inspect the "pocket" in the shoe soles to see if there is any interference with the cleats. If something is obstructing the cleat, cut the rubber away to get a bit of clearance and see if that fixes the problems. Shimano SPD pedals with the proper matching cleats should not be very difficult to release from. A spritz with WD-40 or a silicone lube can also help with both entry and release.