I know this is a broad issue, but it's a big one. When your servers have a lag and/or begin to restart, the infected still seem to have proximity threat to your character even when you can't control them.

For example, last night, I had two incidents where I would "rubber band" during a server issue/lag, the infected would also rubber band, suddenly I am being hit by them over and over but they're not actually near me (or even visible in one instance). Both times they ended up killing me and I could not defend myself, fight back, or run away.

My advice would be that when there's a known sync issue between server and players, perhaps the infected are nullified as a threat. It's frustrating to lose a character after hours of build-up because of that sync issue. This was a problem on the .62 build on PC a while back, .63 on PC (experimental for the past month or two) has been great at avoiding it.