I have just build a new XCP-NG server, with XenOrchestra. I then used CloneZilla to move my Proxmox VMs to XCP-NG. Worked perfect, did not need to even change any NIC config on the XCP-NG side. Machines work i.e they boot and get an IP but they do not pick up their reservation (even though I did change the MAC address in my DHCP server to be the same as that on the new XCP VM. I also checked to see that DHCP was assigning the random IP to a MAC with the same value and it was. Because they are services, I am happy to make them static but I am interested as to why the two machines are not getting the reserved IP.
Sounds odd, I would first mark sure the VM is not over riding the MAC assignment. Make sure the MAC inside the VM matches what is showing in XCP-NG.
The MAC addresses appear to be consistant i.e. not changing. Work has got crazy so I am battling to find time to troubleshoot. Will see if things change after setting up my DHCP on pFsense (maybe my router is going nuts).
I would say if the MAC address matches and you have the right configuration in your DHCP reservation then you might need to break out wireshark and do a packet capture to see what is going on. If you are on linux you can run a tcpdump.