Hmm, I forgot about this thread and just now noticed that it had been updated. RE the question of popping the end walkway off to access the coupler box screw (definitely a weird design choice...) please refer back to this post:
https://www.therailwire.net/forum/index.php?topic=53274.msg729758#msg729758The easiest technique for me was to apply the tip of a soldering iron to the area of the walkway where the glued tabs are on the outer edge of the part (visible in the first photo linked above). This will break the glue joint on those tabs. Then turn the car over and press on the bottom of the walkway with a flat tipped piece of wood or styrene to dislodge the it. (Brace the "top" side of the walkway with a piece of square stock, like in the second picture, so you don't distort the etch when you're pushing on it. I was able to do this without damaging the part, once I had a feel for how much force was required.
I don't really know what to say about the spontaneous uncoupling beyond replacing the couplers with fresh MTL's (or other couplers, like I did). At least you
can do that with the walkway removed. Hope this helps.
-gfh
