OK that is good to know! Not Operator Failure.
Try the lever in the lower (Draft) position, then move the main control lever towards the top of the quadrant. About 1/2" from the top stop the lift arm should start to rise.
If they do not, push the selector lever backwards.
If the lift starts to rise this would confirm that your Position control follower pin is worn or broken.
When you select Position Control with the main lever at the bottom of its quadrant, you should be able to move it slowly up the quadrant and the lift arms should follow it, stopping when you stop moving the lever.
Even if you have an oil leak, the lift should keep "bouncing" as the lift tries to automatically correct the dropping.
Sounds like you are going to have to take the lift off to sort your problem.