Wow! This are may topic from last year!
I had the same problem but with ... computer opponent (yes, computer). In big operation battle from barrbarosa to berlin Combat Mission 2 I saw he turned on some super, hiper, extra modes. Commanded by computer units had ... 9 x PPSh weapons for... german infrantry team (not SMG). Then one of the computer controled panzeschreks was unable to be killed by any of my units! My poor Soviet full ammo/no killed men/SQ was shooting to him from 10 meters - none of panzersherck team members was killed till 3 turns. Then they run away. LOL. In other computer vs human battle some team of "virtual troops" has... 5 x MG's with picture like that mounted on ... tanks! I was playing with no fog of war - thats why found that superb computer modes, phi.
Than such a stupid things I had with almost every one battle played with computer! So my own computer was a cheater? Baaad, baaad guy! lol.
Sbdy told me to reinstall the game - didn't help at all. In CMBO I had... the same problems those days. Computer units that I killed in next few seconds they... standing up. In next turn... they were killed "again" but i didn't do that this time. LOL! No doubt I got some old screens in Interent-Disc - will look for it.
If I remember the only solution was to format/reinstall system and reinstall all CM parts. But thakns to that I dropped CM for much better game: Operation Flashpoint :PP Greetings for all funs.