There are a couple of issues that have come up since 1.5.4 has been released that have been fixed in 1.5.5 (still unreleased at this time).
Roll your FOS kernel back to 4.15.2 to get past the mbr/gpt issue. Make sure you download both the 32 and 64 bit PC kernels (not ARM). Edit the www.conf file to update/include these settings, then reboot your FOG server. pm.max_children = 35 pm.max_requests = 2000 php_admin_value[memory_limit] = 256If you are having issues with multicasting then we will need to have you switch to the 1.5.5 working branch to get that update.