Block backup traffic on wireguard Site to Site when on slow WAN Failover

[ibravo]

We have set up a Site to Site connection using wireguard. We use this connection for regular office traffic as well as for heavy remote backups.

We also have a WAN failover comprised of a fiber connection and a backup 5G service.

When the main ISP is down, the wireguard connection gets recreated on the 5G service, but all the bandwidth is being taken away by the backup traffic. Is there a way to block this heavy traffic over the wireguard interfaces when we are in the slow 5G network?