Error completing areas in forest haven

I have been spending my usal time in forest haven helping new players along for fun.
Tips and healing only. I'm not one for powerlevling, but anyway 3 times yesterday players
couldn't complete the maps due to there being enemies left. The problem is I searched the map
with them and couldn't find anyone left. No red triangles for enemies and since its a pretty easy map
I can be sure there was no one left to kill. Either enemies arn't spawning or something else wrong.
Anyone else experience this?