Remote HA+Z2M and local UZG coordinator over VPN

Dear friends,

I am using HA+Z2M in my main home and I purchased a UZG01 coordinator installed in my summer house. The network is:

HA+Z2M All devices are running on PoE and electrical backup.

For reference, the UZG01 gateway is:

My question is : network monitoring shows 10ms latency and 99,95% availability. Sometimes a down-link happens once a month with wireguard and it takes usually 5 minutes maximum to come back.

What are the recommended settings for better network. In Z2M I configured:
retain: true
with version 5 of protocol.

Availability is set to 20 minutes for active devices and 240 minutes for passive.

What can be done to improve reliability of network in case the coordinator or Z2M would go off? My coordinator is local and the Z2M+HA are distant.

Any idea welcome.

Kind regards,