I was watching a streamer earlier today learning Endless Legend, and he fought a group of lice attacking one of his cities. In the battle map, the lice that was sieging a different nearby city remained visible on the battle map (like a piece of terrain) even though the unit had nothing to do with this battle. It had no effect on the battle but led to a lot of confusion. Such as why he couldn't target the unit, why it wasn't appearing in the turn order, why he could move through it, etc.

A later battle had a similar issue when he fought a neutral (I think) and the lice army graphic nearby on map remained in the middle of the combat map for the whole fight.

I'm not sure if it is lice specific, or any unrelated combat unit, any unit caught in a siege vs another city, or what. But I suggest every army on the map not related to the combat be hidden while the combat is ongoing.