Mystery commander deaths after battle - bug?

[LintMan]

Originally posted by Master Shake:
Could the answer be Decay. If I remember correctly, units hit with decay make a MR after the battle for death. So the commander could have survived the battle, but died to decay afterwards.

The Marignon force had no decay-capable units, and four of the six unexpectedly dead commanders were never attacked at all during the battle, not by melee, missiles, or spells, and they were in perfect health at the end (although they had fatigue at ~100).

Interestingly, on the next turn, one of my commanders was attacked by an asassin. The battle was shown to be in a certain province. She easily dispatched the asassin. When I checked the location of the attacked commander, though, she was in a neighboring province to the one it showed the battle was in. Neither province shows the crossed swords indicating a battle took place.

I'm starting to think my game has gotten a bit corrupted. Fortunately, I'm in the endgame stages now.