Possible cap. Fault?

I have a couple of ATA roller door closers and both have started acting strange within a couple of weeks of each other. 
The issue is the doors (motor) reverses when opening and closing, it will do it 2 or three times then work fine for a few hours with no issue.
It does it every time when the doors m.j or been opened or closed in a few hours.
The curtain is balanced fine and lifts and lowers with ease manually.
Could it be a faulty capacitor or does anyone else have any other ideas?
Please help, I don't want to replace the who unit if not neccessary.