Harvey, I have had this happen twice on my hobby series Vectron. I didn't do anything, but I wonder if the shaft is just a bit short. I've thought about adding a tiny dab of epoxy to one end and after it dries, reinsert it.

Thanks for the advice and observations. I attached the parts diagram, hoping this allows for better description. Possibly something loosened but I think not. Part 6 (screw, 2 of them) hold down the cover over the motor (9) and there appears to be no slack. When the screws are removed, there is some movement possible front to back. When I remove the cardan shaft the part they fit into (no number assigned) easily turns on the motor and the gear. Also, when I do replace the shaft, the loc runs fine for a bit. So, I conclude there is nothing jammed in the gears.

I am going to try adding a little length to the shaft. This will take some time and experimentation.

Regards
Harvey

If the 4 screws holding the pcb board over the motor are fully seated, the motor can't move. I've had to loosen them to raise the motor up to get the cardan shaft into the sockets.

I had the same thing happen with a loco but it was quite a while ago and I don't remember which one it was. But I only have Era I and II steamers. My problem was that there was a small plastic clip which was supposed to hold the motor or shaft in place and one end of the clip was broken. Fortunately it was an available part and replacing it solved the problem.

All, an update

Success for now.

I added small amounts of epoxy on one end of the shaft. My first attempts failed. I repeated this step. I noticed that my test runs lasted longer with each 'drop' of epoxy' that I added. This experiment lasted several days as I wanted the epoxy to thoroughly dry. My most recent try involved placing epoxy on both ends. Each time the amount was very small and so what I added to the length is likely hundredths or tenths of a millimeter. My test today involved pulling a few cars and running at various speeds up and down an incline and on curve and straight sections. Repeated this around 10 times. No failure. So, success for now.

However, I will be buying new shafts and will be inquiring if there exists a next size up.

Appreciate everyone's insights on this.

Regards
Harvey