I hate to be the bearer of bad news but this problem is probably gonna be here to stay
I have a feeling that treyarch not only don't have the time to find the problem with this and may others , They actually don't want to try to fix it .
Every time they have made a patch which tried to fix a few problems , they created more .
For them to try an fix the problem with zombies would take double the time it should , first they would find the problems and patch them .......then spend the same amount of time undoing the last patch with a new patch which might not solve the problem of the first let alone the second patch .
But then what do i know , they could be making a patch to fix all previous patch mistakes as i type