Photo 1 - On the "good side" of the shell, I removed the 2 silver screws and the orange plastic side panel came off easily
Photo 2 - Once the side panel was removed, clearly the gray wire is attached to the screw at the bottom of the handrail post. Note that testing continuity with my meter between the gray wire and any part of the screw, post, handrail did NOT show conductivity. Maybe because it is painted?
Photo 3 - Notice the other side of the shell is different…2 smaller black screws need removed, and a much larger section of orange body comes off as seen in Photo 4
Photo 4 - A mess of wires jammed in this removable shell section in an attempt to keep them away from the motor flywheel. This section of body is a bit fragile in that it is attached to the handrail.
Photo 5 - I looked everywhere for a place where the other gray wire might have been originally attached…the only thing that even came close was the actual bottom of a handrail post inserted through the orange shell that went to an upper handrail on that side of the engine. See where I marked it with the red arrow.
Photo 6 - This stood out because it was the only post that seemed to have the black covering removed and appear shiny. I attempted to tack the gray wire to this post with solder and it just wouldn't take. I stuck the wire under the crossed posts and tried to solder. When I went to put the shell back on it popped off.
Later, a Lionel service station tech told me that this indeed was the correct location for the wire to be attached but it needed high heat and flux to attach successfully.
In the process of all this playing around, the main gray wire broke loose from the radio board. I had to get in there and re-attach it and shrink tube that. While working on this, I couldn't get the excess gray wires to lay anywhere away from the flywheel so I decided to remove the second unknown gray wire completely since it would have been capped anyway and just taking up space and didn't seem to affect antenna performance.
Another note is that there are tiny plastic standoffs at the top of each handrail post insulating the handrail/antenna. These had worked loose and would not stay in position, so a tiny spot of superglue from a toothpick on each solved this problem.
I put everything back together without putting in the 8 screws to the body and did a test run. Everything worked except the squealing brake sounds. I removed the shell again and reseated the top circuit board and moved some wires around to better positions and re-assembled, assuming I would have to RMA it with Lionel. I fired it up and it worked fine, squealing brakes and all, for 20 minutes as I put it through the paces.
Working...for now.
