We moved into an older house a few months ago. The inspector verified
the sensors on the garage door are aligned correctly and that if an
obstacle is hit, the door goes back up like it should. It's a Sears
screw drive opener.

Recently we've been having a weird problem. The door starts to close
and then at various locations it then starts to go back up again as if
it hit something. It could be partially closed at various points like
1/2 way down, 3/4 way, 1 foot to go, etc. We have to sit there and keep
hitting the button and eventually it will make it all the way closed.
This doesn't happen all the time which is what makes it frustrating to
figure out what's wrong.

I have checked the sensors and they're aligned fine. I noticed that the
sending sensor that is installed on the rail was bouncing a bit when
the door got close to the ground so thought maybe that was breaking the
beam. I took it off the rail and mounted it on the wall so it's not
moving at all now, but the problem is still happening.

It's an older door, probably the original from the early 80's, and the
wheels seem to be gliding somewhat smoothly through the rail. The door
does shake a bit when opening and closing. Before I call a repair
company, is there anything else I can try?
Thanks,
Jeff