Rediculous number of enemies (bug?)

[Dragoninja54]

I was in a run with a nice build and I was having fun but around the 20 minute mark, before malphor even spawned, the number of enemies insanely skyrocketed to the point where there was maybe 100+ enemies on the screen, every inch filled and there was just absolutely nothing possible to do. I wish I had taken a recording of it so you could see what I'm talking about, but I swear I'm not just crazy, it was an ungodly number of enemies. I'm pretty confident it was a bug but its a bummer because I really liked my build.

[Dragoninja54]

I was on SMG, my enemy spawn rate was only 110%, so I don't know how it happened