'96 Ls Rear Cupholder Wont Lock Into Place

[xndr400]

On my '96 LS400, the rear seat cupholder was stuck in place, probably from dirt and soda from the previous owners kids. I finally forced it to pop out. Now, after a bit of cleaning, the cupholder retracts and extends freely, but now it won't lock into place inside the armrest, which means I can't put the armrest up. I've done a search and have seen several posts on how to get the cupholder unstuck, but nothing on how to get it to lock again. I know the cupholder and rails assembly can be removed from the armrest, because you can order a new cupholder assembly from Lexus. But I can't find any information on how to get the darn thing out. The service manual has absolutely no information on servicing the armrest. The parts catalog shows several screws that hold the rails in place, but I can find no info on removing the cupholder to gain access to the screws. Has anybody here ever dissassembled the rear armrest and if so how. Thanks