I has seen the same thing happen. Zombie running down the hill suddenly falls over on it's face dead. Scared the crap out of me becase I wasn't sure whether of not it died spontainiously or a sniper took him out at long range and i was next. I got the hell out just in case.

Same with me... directly at connection regardless of server the FPS fluctuates between 7 and 12 with drops to 1 FPS. Freezes and manual termination of game were common. Interaction with Zeds was almost suicide and caused character damage due to games freezes of up to 5 seconds. The games is basicly unplayable now.
Character was fully kitted out and the two servers played had 1 and 0 additional players hosted.