All of my saws have done that at one time or another....both the Dewalts and the Excaliburs. The Dewalt repair place said that if it stops at just the exact wrong spot, it won't lift and you just have to tension it back up, turn it on and off quickly, as a previous post said. Nothing needed fixing, it's just that at that exact spot, for some reason it can't fully lift. Just another quirk to work around.
Nancy