Zenwoks 7 sp1, PXE imaging.

We have 400+ PCs of various makes and models. They all PXE boot for Zen
imaging. 3 out the 400+ keep imaging when set to PXE boot.

The only thing that seems to be an issue is that the Image Safe Data is
NOT being written on 3 problem ones. Even when I use zisedit or ziswin,
the settings do not stay. I have tried wiping the ZISD but they still loop
and still ZISD does not get written.

2 PCs are identical make and model, but I have a 100+ of the same that are
working normally. The 3rd one is newer, but I also have 100+ that work

What else can I look at??