I think I overstated the inspection difficulty. As the bed is being raised or lowered, you can peek over the mattress and using a flashlight see the horizontal member with motors on each end cranking their way up and down most of the traveled racks fastened to the outside wall. If you look through the gab below the bed platform, you can see the lower end of the racks. You should be able to see damage or irregularities in the rack slots that are gripped by the gears on the motors. It is also possible to get some lubrication in there as needed.
Whoever did the "rebuild" (whatever that means) should have tested the full range of motion and fixed that seating problem. Could be the bed board was not positioned properly on the rollers or there is some kind of obstruction which causes the current limiting switch to go off because of the resistance before the end of the bed bottoms out. I'd just take it back and tell them to finish the job.
Position the bed about 2/3 up or so and look through the gap below the end of the board to see if there is anything in the way. It's supposed to come to rest on the two aluminum square tubes and then flip against the wall.