I just noticed and submitted a bug report for this same issue. I believe it was on the Ghost Ship interior map. It also caused my NPC BOffs to shoot through walls and not follow me properly, get stuck on corners, etc.
I'm getting the same thing on the War Games interior map. Combined with the screwy pathing, I'd guess it's something with the parameters of the maps not being fully defined in terms of what you can and can't move or shoot through.
A couple things to note.
1. When you're in Preview Mode, pathing hasn't been generated yet. This may cause strange behavior with AI knowing what's in their line of sight.
2. If you put NPCs inside a building on an exterior map, they're going to fire out at any enemies within range. This is not something on our fix list; they can see you through the inside walls, which is supposed to happen.
3. There are certain walls that are one-way. Hop into Preview and view it from the enemy NPC's side. If it's one-way, then enemies will be able to see / shoot you through it. (You can counter this by dropping another version of the one-way wall and rotating it by 180 degrees.)
If enemies fire at you through walls that are solid from both sides, then please make sure to mention which map it's on, what wall piece is being used, etc.