Surge Problem - neverending surge

Game mode: Online Official PvE Europe Enhanced edition

I summoned a surge, fought NPCs and after a while I headed to my wheel of pain with a knocked out NPC.
A few of the enemies followed us, one got stuck on a rock. I tried to kill him but he fell down - apparently probably into the huge rock.

So it’s been an hour now and the purge is still running - probably forever until the next server restart blocking others and myself from using that surge locatin.
Problem is: as long as any of the NPCs are still alive the surge won’t continue

Solution:
Either have all the summoned NPCs check every 5min or so if they are too far from the pads on which they spawn (more than 10m away from the borders of it) → then teleport them back onto it. Problem solved
Or each wave can take at max 15min before the next one starts.

I prefer the first solution.
And give a max time for a surge. if it takes more than 1h stop it.

Can the AOE from noxious gas arrows or gas orbs start draining that NPC’s health?