Backup and root quota on XFS

Hi ,

I'm having a strange behaviour when perfoming a virtual server backup.

I've a /home partition where the virtualserver user data are stored with quota enabled.

When I perfom a backup, at the end of the process, the root user quota becomes 1Gb instead of unlimited that was before starting it. So it cause a disk quota error when the next backup is over 1Gb.

I'm using the latest version of Virtualmin GPL on a updated Debian 8.9 and the /home filesystem is XFS.

Any ideas of what can cause this behaviour?

Thanks

.nicola