Garage door problems are on the rise and mine is experiencing another one.

This morning, the door went up and stopped about 3/4 open. I lowered it with
the remote, then reversed to open again helping it along by pushing it up.
When leaving for work, it would come down a partial way then go back up. I
didn't have time to troubleshoot until now (after work).

This morning, I removed the center connector of the door to the opener for
manual operation. Upon troubleshooting just now, the opener has a travel of
about a 1 to 3 feet. I push the remote and it moves down, stops, then moves
up on it's own. I disconnected the limit switches and tried again. The same
thing happens. I increased up and down force but nothing. I know it's not
the door causing the problem for many reasons but obviously, the main reason
is it's disconnected. Therefore, it's in the opener itself but I have no
idea where to even look. All gears, chain links, tracking, teeth, etc. are
lubricated, intact, secure, etc. I'm dumbfounded. Any suggestions?

Thanks