TMCC Signal/Track Voltage Loss

Some engines have a weaker signal reception than others. I would try running additional hot and ground feeders to the spots that give you the trouble. This would be the easiest to start with.

Rod Miller

if you put your hand over the engine does it come back to life?

 TMCC signal loss usually has a flickering headlight. Placing your hand over the engine will correct it. The fact that it's powering down it sounds like a power issue. I'm guessing that this engine being an ABA it has at least 2 powered units. Not familiar with K-Line diesels. Are there tethers connecting the units together ? Is the problem area on a curve ?  The tethers could be working themselves loose. When you move the engine perhaps they are reconnecting. I'm guessing there is only one TMCC driver board in one powered unit if they are tethered. Can you run that one engine on it's own to isolate the problem. 

 The fact that you are moving the engine slightly. Tells me more that the wheels even though they are clean might not be contacting the rails well enough. Not familiar with Fastrack. Are both outside rails connected to one another ?  Often times with traction tires getting a good connection from wheels to outside rails can be an issue. Especially in 3 rail where there is significant side play to slow running on tighter curves. I had a MTH DL109 that stalled everywhere. A slight jostle and it would be up and running again. Finally after a good break in the problem went away.  

Run the engine with only conventional if it does it still you may need to readjust pickup rollers to right or left 

Running conventional is a good idea to check track voltage, but if other trains run thru fine, track drops are probably ok.  Sounds like an engine related issue with pickup continuity or ground connection.  G

Dirty wheels or track.  Are the feeders in pairs?

Since other engines get through fine, focus on the engine A units. Sound like a ground (common) issue. Loose ground wire on axle touching hot coming out of a curve?

My Weaver U25B does the same thing. I did notice where it does it is where the track is not flat on the table which makes me wonder if the roller contacts are not touching the track at that point. If I move it slightly it comes back on and it only does this when the engine is crawling.  My solution was to run the engine a little faster over the spot.

The rollers did this on my Lionel SD 80 when slow it would just stop I would tap the engine it would power up the rollers have side play just grab it and move them just slightly side to side it fixed my problem