Sudden Death Blitz - FPS Drop

Pretty much what the title says, not sure if i'm the only one getting it, but after about waaaaaave 28/29, when scramblers and Blackjacks spawn 24/7, I get really choppy FPS and from then on in waves it remains.

Prolly just the processor/GPU getting overloaded from items on the screen, but it's a minor annoyance.