About 2 days ago I ran lab 3 and I've been bothered by an unnatural thing that made me have to spend an extra half hour in there. The doors that need the door handle keys USE door handles when they are closed. I killed a hara and grabbed the last key but more of them were still behind that one. I went in and shut the door behind me so they could not follow, then I went another 2 doors in and realized I used 4 keys. The second one I used was on the first door, to shut it. I went back out and rushed to try to get 2 keys before they automatically shut. I did not receive a door handle key for several kills and by then the doors shut.
I had to collect 5 extra keys to make up for the 3 I used walking in, 1 extra on shutting front door, and 1 extra on opening it again to go quickly get keys.

I think doors do not need keys to be shut and this feels like a bug.

How did you get into a situation that there were mages that could follow you into the tool-locked doors...? I thought there were no-monster tiles preventing leading the Spellcasters out of their rooms? I could be wrong on that one.

I shut the door before they entered the room, they were coming toward me and I did not want to deal with them.

And this was at the first tool required door? There may be an actual bug with the no-monster tiles, but I'm pretty sure opening/closing those doors has always required a tool and it was made that way by design. I certainly remember getting in trouble back in v2 for lagging out of the last tool door room on my templar due to not having enough mana to recall. Not saying it was -good- design, but by design nonetheless.

I still have trouble trying to figure out where you were when this happened because if I remember right, the Spellcasters inside of the tool doors don't attack you or move at all until you engage them. That, combined with the no-monster tiles keeping the other Spellcasters away from the "main hallway" where the shops are, sounds like a bug or missing information relevant to the story. They were put that way specifically to block the doors so you couldn't bypass them to get the last key without aggro'ing them. Did you aggro one and try to get past him then get attacked by the second one because you were in combat with the previous Spellcaster? If so, sounds like intended behavior of the monsters and doors.

No, I was not aggroed to the spellcasters inside of the tool doors. Enemies from outside the tool doors were chasing me still as I ran into the first tool door, I shut it behind me to keep them out then walked on another 2 doors and realized I used 4 tool doors by the time I reached the first spellcaster.

I think the item (tool or key) is consumed by "using" the door, whether it is open or closed.

There is one Spellcaster Guard outside in the corridor.
I have added some no NPC blocks so that he can not follow you into the tool door rooms.