Senior Moment?

Only thing might be a short that appears when engines motors or trucks move to some position that grounds out the power and instantly trips breakers.  Or something metallic hanging from a car or engine "underbelly" that shorts out track.  Or if using conventional tubular rail, a center rail insulation piece shifted out of place. 

Not familiar with Android app so cant explain mysterious engine disappearances.

Sorry, not more helpful

I've been trying to avoid removing the Alco PA from the track since it's a PS#3 ABBA.

Yeah not fun... however you may have to, find an old towel  to lay them on... try again with the other engine....  Having the Alco coming up as a GP-9  happens occasionally when you try to add engines with other engines powered up on the layout.

 (  My son thought   I  should have  an Android and gave me one but I  but no intentions of ever using  it  to run my trains. That's  what I call a senior moment.)   Gregg AKA grump.

Can you roll them over slightly with a towel for support and insert a piece of paper under the rollers?

Closer exam with the shells off found a tiny piece of ballast stuck in the gears but after it was removed they still run less than a foot before they shut down so tomorrow they're off to Mercer Junction to be looked at. I don't know enough yet about these yet but when turning the flywheel on 2 of the motors I can feel a flat spot. That may be normal.

Thought I might have had one too many senior moments. Worried, went to the doctor and he told me, "forget about it."

I would unplug a unit at a time and see if they run B-B-A, then if no improvement, B-A, and finally just the lead A. Can always do an A-A last. There should not be a hang up when you rotate the flywheel, maybe another piece of ballast? Misaligned motor and truck assembly? Keep us informed of your solution.

Unless I'm mistaken again both A units have to be connected for this to run. They won't run individually

The lead unit should run by itself, just a matter of removing units to see where the issue is.