My garage door would open 6 inches and stop; then a foot and stop; then about 4ft and stop. then all the way. It would cycle like this whether I use a remote or the inside button. mostly, it now will not open all the way unless I physically assist by pulling up the door as it was cycling open, and then it would open all the way up. The spring and cables are 4 mos old, and there is no blockage on the rail that I can see, and power seems constant.