I have several MTH PS2 diesels lettered for my railroad of choice, the Pittsburgh & Lake Erie. My layout uses postwar style tubular track.
I have two spots where my diesels regularly stall. They hit these spots, and stop dead. The motor with the tach strip continues to spin, the wheels spin, the other motor stops and the engine does not move.
Over other parts of the layout, the engines run fine. I originally thought the problem was with the engines so I spent time checking the motors and looking for bad solder joints or some mounting problem.
I finally realized that the motorized truck was actually riding up somehow and lifting the wheels up enough that they lost traction. I’ve now seen that this is a problem on many of my diesels.
In the attached PDF file, I show what I did to fix this problem.