Take a look at your door springs. Sounds like one might be broken. Also remove the cover and look at the drive gear. It is white nylon just in front of the motor and may be stripped.

Thanks Don, I will check both.

Don 1, The door springs look fine however the large white nylon gear is stripped. In the bottom of the case was a lot of white pieces and dust. Is this something a basic handyman like myself can replace or do I need to get a pro involved?
Many thanks,

If you are a handyman you shouldn't have any problems doing this. The parts come with instructions. The part number is 41A2817 and is available at any good door service company.