I've got the same error.
I didn't delete any chunk, what can i do ?
i use env vars
export PBS_REPOSITORY=
export PBS_PASSWORD=
export PBS_FINGERPRINT=
than i try to use
proxmox-backup-client backup tms_psql.pxar:/opt/data/tms
and i got
proxmox-backup-client backup tms_psql.pxar:/opt/data/tms...