@RobWhalley I think in the beginning i had that option enabled in my backup jobs, but found it was a hassle to move VMs between hosts with it on so i turned it off for all backups. Might be why my jobs worked because i had already done that switch in the past.

posted in the other thread as well but Xen Orchestra, commit 1a7b5 backups are working again. I tested configure and vm backups. They are being backup to NFS share.

try downgrading your nfs to use version 3. I think version 4.x has performance issues.
in you settings-->remote, you can edit the nfs mount for backups and add in the -o options section.

I dont know the exact command but you can try using nfsvers=3 and see if that helps.

scratch that prior comment. My backups are all setup as delta backup with schedule 2nd run that forces full backup. So i believe both are working correctly.

if you can also try deleting all the backup snapshots of the VMs in the backup and running full backup then the delta backup jobs.

looks good
Xen Orchestra, commit 384bb
Master, commit 384bb

thanks for quick fix