Auto door has problems

[mphkim]

My auto coop door runs side to side with drive shaft bolt and runs on battery 12volt like for a lawn mower. Have replaced motor, drive shaft and battery. What is name of part pictured below?

 

[cavemanrich]

I can only take a guess and say it looks like a Limit Switch, that controls when the motor should stop moving door.
First... what is the problem you are encountering???
Would be good to know which door you have.(manufacturer name)
Can it be that the problem is caused by a buildup of debris especially on a horizontal door. Very possible, since the bottom track can catch a lot of things.
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, and

 

[mphkim]

No it is not a limit switch, it is square nut for drive shaft. Door seems to have dropped and works when you hold door up in track but if alone the drive shaft just runs and runs and never catchs on door to pull open or closed. Just need name of this part!