Taking apart a BR50 and not finding anything wrong

When I put Maerklin 37819, engine 051 013-1 on the roller stand yesterday, it wasn't recognized automatically by the Mobile Station. At all.

Another locomotive was programmed just fine, so it wasn't the overall setup. Tonight I double-checked connectivity, checked the wires, checked the decoder socket, swapped in another decoder, nothing. I tried the decoder in the BR 50 with cabin tender and it worked there, so it wasn't the decoder (whew!)

I slowly took apart 051 013 until I had the naked engine in front of me. I checked the cable connections, double-checked connectivity, put it on the roller stand. ... And it worked just fine. Slowly and carefully I put it back together, and ... it still runs just fine.

Maybe user error and I didn't press Stop on the Mobile Station to let it detect the locomotive? But then it should have worked with the decoder from the other BR 50.  I have no idea. At least now I know how to take this engine apart and put it back together. The fine wires sticking out underneath the boiler make reassembly quite tough, since the wires kind of need to be pushed aside on both side to not get caught when reseating the boiler on the chassis assembly. I ended up canoodling the engineer's side into place first and then do the fireman's side.

Since I had the boiler with the cab off, at least it was a convenient time to install Preiser figures for engineer and fireman. I wanted the engineer to have his elbow on the window sill, so unfortunately he had to loose his shoes and feet. I used canopy glue to keep the two guys in place.