The guy who installed my16x12 door talked me out of a jackshaft opener. He said that he had seen the shaft twist on the big doors causing it to operate unevenly and bind. I like them better than a chain drive but was afraid not to take his advice.
sounds like a lazy install guy who couldnt get the cable and springs right.
No, they installed the door about 4 years before I had them to come back and install the opener. They do great work and do a lot of installs in my area. He just said he had seen the shaft twist after extended use on a wide heavy door. It doesn't sound like a widespread problem if others are not having the issue.