Hi, my name is XXXXX XXXXX I will be helping you today.
Sorry to hear about your garage door opener problem.
The opener may be trying too hard to open the door either because the spring(s) is weak or broken or the tracks/ rollers are bent or need lubricating. If the opener is humming, I would definitely check these out. The opener does not do the heavy lifting of the door, the springs do all the work, the opener just aids in moving the door open. I would verify that the cables to the springs are still on the pulleys (if you have this type). I would also verify that the door is not going up slightly crooked, just enough to bind.
Perform the following tests:
First, I would close the door and then disconnect the door from the trolley and operate the door manually. The door NEEDS to roll smoothly and not bind on anything and it NEEDS to be balanced and stay at any point you stop it. If the door wants to go down by itself the springs are weak and at fault; have a qualified service technician fix/ adjust them...they can be very dangerous to work with since they are under extreme tension.
Second, operate the opener without the door attached and see if it operates correctly. The trolley will fully go up and down if working properly.
Performing these tests will help narrow down whether the door/ tracks or the motor unit is giving you the problem.
Please let me know what you find from these tests and we can proceed from there.
If you need further help or clarification on this answer, please do not hesitate to reply to this post.