@farokh one backup job should leave one snapshot. this is the way. to differentiate from previous backup the data to be put in the delta, it has to refer to this snapshot. delete it and you get a full backup ongoing. if you have two snaps on your VM, either you have a manual one, or you have multiple backup jobs backuping this VM (check the backup tab of the VM ?)

@Pilow Double checked. There's no filter in place and no new VM.

FWIW The Migration tool doesn't seem to work for me for warm migrations for standalone (single dell server) Esxi 6.5 to standalone XCP-ng 8.3 and the latest XOCE. The account of migration of 3 servers is a follows; Guest 1 - snapshot, ran the XOCE migration, waited 4 hours observing the disk copy progress, then nothing. no final snapshot, no task completion. Started again as a cold migration completed and then had to rename VM and disks from delta labels given during migration. Guest 2 - snapshot ran cold migration and on completion then had to rename VM and disks from delta labels given during migration. Guest 3 - snapshot ran cold snapshot ran cold migration, one disk completed, second disk didn't with task destroyed due to exceeding the 24 hour task limit (assumption). The 24 task limit is a bit annoying, but I have made the config change to give it another go this weekend. The tool made the migration less fiddly but the issue with the warm migration make it a higher touch experience.