The bunk uses the same Schwentek-Lippert system as the slides. The system has two threaded racks and two synchronous motors with gears that ride in the toothed tracks. When you operate the switch, 12 VDC is applied to both motors and they run the gears in both tracks of the bunk lift or the slides.
The key word in the description is SYNCHRONOUS. It is fairly easy to get these two motors out of sync. When that happens one side will lift (or slide) farther than the other side. In some cases, the out of sync will actually jam the slide or the bunk and not fully retract. If the power is not removed from the motors damage to the drive gears or or the toothed rack can result.
Schwentek (and many of us owners) always tell newbies to not lower the bunk or operate the slides partway. Running the motors part way and then reversing them is a quick way to get them out of sync. Here is a link to a YouTube video explaining how to retime the motors to get them back in sync:
In the manual I compiled after much research, I recommend not operating the Schwentek system on the slides or the bunk partway. You just increase the risk of getting the synchronous motors out of sync. In addition, as Schwentek also recommends, when operating the system hold the switch to lower or extend until the motors stop and continue to hold the switch for an additional 2 or 3 seconds after the motors stop. When retracting the systems hold the switch to retract and continue to hold the switch for 2 or 3 seconds again after the motor stops.
Also, on the bunk be sure you pull the two safety pins on the passenger and driver sides. You also have to lower the two captain chairs backs to full recline so the bunk does not hit the top of the seats. Also if you have something behind the driver's seat or passenger seat (like a trash can) move it so the bunk does not get jammed against it. (That would be good old experience talking there).