By default in PXE service startup the service itself adds DHCP option 60 with the value PXEClient to DHCP server options. Atleast on our environment there is one scope which does not tolerate to have that value set as it has own PXE environment and that option prevent it to work. I heard from support that you are using the Microsoft PXE services on background which makes that option. My suggestion is to add registry entry(or some other method) to control whenever it should be OK or not to have that, if set it would delete that entry after MS has added that into DHCP server. I have made that check in the powershell script which looks that value every 5 minutes and if it comes back it will remove it, but it would be better only delete option when service comes up.