Never Assume (twice)!
The SP AC-5 4-8-8-2 used to haul the 18 passenger cars but I had to remove 4 of them to make the grade. Initially, I assumed the track had oil on it and needed cleaning. Turns out the cars developed a lot of drag.
The trucks pass the electric to the lights via metal journals and, after several runs on the layout, they needed oiling. Normally, I never lube axles as they usually stay friction free. These are the SP unit passenger cars by BLI. I checked the enclosed packaging and no suggestions on needing oil.
2nd assumption: new circuit boards are more reliable than 40 year old contact switches! I spent about an hour trying to 'make' the old contact switches for my turnouts that send a signal to the LCC boards but found out the circuit board had a defect for one lead. Only way I found it was swapping two of the input wires to the circuit board and the problem stayed with the respective circuit board's input.
After each power up, the power cat-5 cable has to be disconnected and reconnected to the LCC tower board to initiate proper operation. If not done, the signals don't respond. There is a yellow LED that flashes indicating a problem. The CAT-5 cable runs about 150' to connect all LCC boards so the distance may be a factor. I have an additional power source that I can add to break up the total run. It's no big hassle to do for each startup of the system but something I always need to remember to do.
Testing the SP AC-5 and passenger train.
Some rail adjustment needed to prevent front drivers from lifting at this one spot.
Long reach to spike rail ends so the lead truck doesn't pick it. Some white foam helps protect my knees and hands.
Stock rail a little too wide for lead trucks.