Sounds like it is hanging up somewhere. Sometimes one or more rollers will have the bearing go out on them which causes the door to bind up. Replace the ones with lots of play and oil the others. Make sure your rails are still aligned properly.
It has an adjustment to give it more power to open the door but increasing the power make not fix the problem. 3in1 oil on the rollers and the chain would be ok. Check all door section mounting bolts. Sometimes the door motion causes the nuts to come off and then loose mounts may cause the door to bind up. All I can think of for now. Good luck.