Lost MFX Locos

Sometimes when placing an MFX loco on the track, the familiar registration process just doesn't happen. On other occasions a loco which was running happily last time you had a "session" no longer appears on the loco list.  The net result is the same:  The Preiserlings never get to go for a ride on their train, and they finish up the day all grumpy, demanding ticket refunds, meal allowances and goodness knows what all else. 

One of the causes of the problem seems to be an “interrupted” initial registration:  If a loco is placed on the track to register it and the process is interrupted in its early stage by (for example) a short circuit elsewhere on the track, or the loco being jiggled while it is being placed on the track so that the initial contact is "bounced" a few times, that seems to bring the problem on.  For this reason, I like to stop other activity on the layout to eliminate electrical noise when registering a loco (although this may not always be possible if it’s an exhibition layout for example) and if one can press stop (although the same constraints may apply) while actually placing the loco, that makes a clean start too.
It's possible that an incomplete loco “delete” is also a cause of the problem, and certainly the symptoms are the same even if the actual state may not be identical.  This may explain why sometimes the "recover lost MFX Loco" function on the Central Station seems to work as it should, and in other cases it just doesn't seem to help.

The CS2 and CS3 both have this "recover lost MFX loco" function built in.  Use of the function is covered in The Digital Club newsletter vol 31, #1 for Jan 2019 so won't be repeated here except to say it's certainly worth a shot, but in my experience, sometimes it works and sometimes it doesn't. 

What always seems to work for me is to take the offending locomotive and place it on a track with a different controller.  Let it register there, then move it back to the original controller.  The decoder and/or controller seem to recognise that the original pairing is no longer valid and it then re-registers normally.       

Note that the “different controller" can even be almost anything: a 6021; an intellibox; another CS; or even an analogue transformer - if the latter then just run the loco in analogue mode for a few seconds (best to avoid hitting the reversing pulse button though) then place it back on the digital track.

It's possible there are exceptions where the foregoing might not work, but thus far I don't recall ever failing to get a loco to re-register by this method.  Try it.