I’ve been having the same issue with the G8 ProBooks and have finally got one to image throught the NIC however I’ve been through many steps so I followed this guide
https://docs.fogproject.org/en/latest/reference/compile_ipxe_binaries.html
I then re-downloaded & re-installed FogProject from github.
PXE is noticably faster and so far so good.
Whether compiling and copying the ipxe worked or whether it was the re-install or a bit of both I cannot say.