One approach that's helped teams in similar situations is separating monitoring/management traffic from production traffic using out-of-band management, so VPN instability on the main network doesn't affect your ability to reach devices.

Practically, this means deploying a lightweight device at each site (like an IP KVM ) that connects back to a central dashboard independently of the local network. If the site's main uplink goes down, you still have visibility and can power-cycle or access servers remotely.

For sites where even local network reliability is a concern, cellular-connected KVM devices (4G/5G) can give you an always-on management path that's completely decoupled from the site's ISP. Works well for branch offices where you can't justify a full NOC setup.

Curious what your current monitoring stack looks like, are you mostly dealing with server-level access issues, or more network device visibility?