Could be. The thing with this mission is, a while after you kill the mobs in a corner, more will spawn in that corner (up to a certain point, it is possible to clear the room). So if OP had completed the mission up to where you get the clump, it's possible that a bunch of mobs were waiting in the starting corner.
If that's the case, a better mechanic might be to reset the room completely after player dies?
Of course, 'running diagonally' not a great idea, as is wanting to finish the mission without disengaging the auto pilot in your head. If you pay just a little bit of attention, it's pretty clear that this is not a return item mission.
I actually like this mission, it's different, and i definitely got a kick out of it the first time I did it. Now we need moar so it's not the only one that comes up all the time