Heard about 2 ways of fixing this annoying, game breaking issue.

Preventing Hittable Desync
The -lv parameter (low violence) setting makes common disappear when they die, but I've heard that it prevents desyching and for as far as I've been using it its worked.

Steam>right click Left 4 Dead>Properties>Set Launch Options>-novid -lv

Fixing Desync when it happens
Recording a demo puts the hittable back where it should be. You can keep gore, but the game freezes for half a second to set up the recording.

bind "z" "record hittablefix;stop"

Edited once, 3/4/11 - 5:50pm.

I like the subtle inclusion of novid in there :3 Best command

Good tips!

Cheers brah!

+ Rep

+ Restecp