It is helpful if you still have the installation manual, but if you don't, you should be able to get help from GENIE directly. In any case, you will probably find some adjustment screws on the rear of the motor body. They are for pressure sensitivity and should be adjusted so they don't kick back too easily during door operation. On the other hand, you want to make sure you don't have the door set so it can crush an aluminum pop can when it closes.
There should be two screws, one for the opening cycle, and one for the closing. Adjust it just so it doesn't do it any more.
You also want to make sure there is nothing blocking the door track and that the door itself operates without any snags or hangups, and that the springs are adjusted so the door has basically neutral weight at all positions. (The door should stay where you leave it in all positions. Pull the red release handle and operate the door manually to check this.)