Not as easy to do when the boat is on a lift or in the water, as compared to up on a trailer - but I once had a drive that needed some “encouragement” to drop from the full up position, even though the pump was working fine. So I would stand on the drive and bounce around while someone else had the down button depressed. always freed it up. I forget what the permanent fix was, I guess I replaced the entire pump assembly, and that fixed it.
careful if you try and force it. I’ve seen people do some serious damage to the transom assembly ( that required engine remeoval) trying to force a stuck drive. I believe putting weight on it only helps if it’s stuck because of a hydraulic issue - if something else is causing the problem, and you force it, you may be sorry. Might be better off running it to the shop on the other motor?