Yes - some weirdness in the core code which cannot really be cured. (I have tried to find it, but it is one of these random things that you cannot get repeatable enough or reliably appearing enough to debug properly. It seems to me to happen more often to a section that has e.g. travelled > 6 MP on a vehicle then debussed, than one which itself walked 4 or so hexes, but again - not repeatable enough to properly set up and breakpoint in the debugger. Any save game (not a PBEM one) where it can be reliably repeated would be welcome! )
So, sometimes a successful rally
will return a section to full MP.
Consider it to be led by a really good/lucky NCO!
Cheers
Andy