Reducing the log file size on the DC may help with this, it did in my case.    See options here:  https://documentation.meraki.com/MX-Z/Group_Policies_and_Blacklisting/Troubleshooting_Active_Directory_with_Group_Policies ... View more

The settings below have worked perfectly for me to boot a phone on a Z1/Z3 from a remote PBX. Similar settings should work for a PXE boot.   ... View more