I was sure I reported this before but I can't find it.
When I do a quest and enter a battle as part of that quest, I then return to the strategic map. When I do so, the army on that tile will have an icon above it signifying that there are multiple armies on that tile. As soon as I move the army the icon disappears.
Likely this occurs as you are literally spawning an enemy army on top of the army, which causes the icon to appear. It is then not removed properly when the battle is done.
