True, I have had a couple turn into crawlers and lunge, just bad luck on that. Luckily I haven't been killed from one. I play insane all the time, but I only survive for days, most times for hours before a swarm gets me and I get trapped. Stay away from the trees, they pop out all the freaking time. Stay with a quiet weapon, the noise of gun fire on insane means death. Get that Sneak, Nimble and Sprinting up fast. Carry a back up weapon all the time. And remember there's always, ALWAYS a zombie behind you.