I have a Proto 1000 RS11 locomotive with pickup problems. I have checked the internal wiring, and found all four truck frames securely wired to the light board. The engine gradually starts stuttering. The light flickers, and at first it stalls mostly on turnouts, but shortly it will stall absolutely anywhere. It first started happening when I lubed the axels - bad move! I have since then cleaned the axels with denatured alchahol several times. I can only get a few hours running time out of the engine before it needs to be cleaned again. I’m running the axels absolutely dry unless there’s some residual oil inside the little square blocks which slide up into the truck frames.
The problem may not be with the axle-to-block connection, but rather with the block-to-frame connection. I’ve got a Bowser PCC car that had that problem. Once again, take it apart and clean it. You should be OK with a little light lubrication of the axles.
I’m pretty sure I can rule out dirty track - all the other engines run fine. I also think the wheels are pretty clean. They got soaked in alchohol along with the axels, but they looked ok even before the dousing, and the last time this happened, I cleaned the wheels first with no success.
Next time, I’ll look harder at the interface between the small blocks and the frame, but I wouldn’t suspect a problem there.