A similar thing was happening to me. Over time our garage door started to shimmer and shake as it rose or lowered. Sometimes the indoor wall switch did not operate very well. The door and opener had been replaced 11 years ago. Like other mechanical items it was beginning to wear. I didn’t know that a sagging chain indicated a possible problem. I called around town and found someone who would inspect, adjust and lubricate our garage door for $49. He offered to replace the indoor wall switch for an additional charge.
We have a LiftMaster Door opener and fortunately the serviceman is also a LiftMaster sales representative and is very famiiar with these door operators. He took one glimpse to advise me he suspected a problem he has often seen. It is common for a specific part to wear out. It is indicated by a sagging chain. He removed the cover to the opener assembly and even I could tell that a part was worn and needed replacement.
Within a half hour he replaced the parts and lubricated the door. It now works as smooth as silk.
The lesson? Bonney and I need to take some time periodically and look around the house. Over time the things we own have become worn, in need of repair, and sometime should be replaced. It’s possible for the frog to jump out of the cookpot before he cooks. So it is with us!.