mhmm.. can you post your versions ('proxmox-backup-manager versions --verbose') ?
i'll see if i can reproduce that here...
edit: also did you restart/reload the proxmox-backup-proxy inbetween ?
I didn't restart any of services, they didn't crash either.
● proxmox-backup-proxy.service - Proxmox Backup API Proxy Server
Loaded: loaded (/lib/systemd/system/proxmox-backup-proxy.service; enabled; vendor preset: enabled)
Active: active (running) since Sun 2022-05-08 01:40:14 CEST; 3 weeks 4 days ago
# proxmox-backup-manager versions --verbose
proxmox-backup 2.2-1 running kernel: 5.13.19-1-pve
proxmox-backup-server 2.2.1-1 running version: 2.1.1
pve-kernel-5.13 7.1-9
pve-kernel-helper 7.2-3
pve-kernel-5.13.19-1-pve 5.13.19-3
ifupdown2 3.1.0-1+pmx3
libjs-extjs 7.0.0-1
proxmox-backup-docs 2.2.1-1
proxmox-backup-client 2.2.1-1
proxmox-mini-journalreader 1.2-1
proxmox-widget-toolkit 3.5.1
pve-xtermjs 4.16.0-1
smartmontools 7.2-pve3
zfsutils-linux 2.1.4-pve1
$ proxmox-backup-client version
client version: 2.1.2
My PBS client it it's any help was installed from
https://github.com/sg4r/proxmox-bac.../v2.1.2/proxmox-backup-2.1.2-1.x86_64.el7.rpm