I have noticed the same thing; I also did a clean install and it doesn't change it. I have tried multiple settings and nothing. The only difference for me, however, is that the zeds seem to be fine in the beginning of my gameplays. They are outright dangerous and I have even died in the first few minutes due to bad decisions, but then as the game progressed they became just nothing... slow, unresponsive. They seem to hear me and come to me just fine, evening breaking windows and doors, but they don't attack/bite/scratch. I have had them literally in the safe house kitchen just standing there doing nothing while I looted, moving around to my sounds like... well, zombies lol... but no attacks. I tried all different settings for memory, sight, smell etc and it's all the same, they start out good and then just stop after a while. I have a theory that it may have to do with sleeping, but I am not sure, since it appears they go blank after I survive the first day, but it could happens earlier or later I haven't taken note.
