Why do we lose IPSec connections and can't re-establish them?

We have tens of IPSec connections between our office and customer sites. At the office we use pfSense V2.4.5 as VPN gateway and placing Ubiquiti Edgerouter X devices with the latest firmware on the customer sites to establish the connection with. The Edgerouter X always establishes the connection as we not always have the possibility to forward ports on the customer network(s). It does this by pinging a internal ip on our office site once every minute.

In general the connections are stable and everything is working fine and like expected, though some times a connection is lost "randomly" and doensn't come back. I can see in pfSense (System logs / IPsec) that the Edgerouter tries to connect to pfSense.

pfSense log:

I don't understand what happens here as this specific connection worked fine and stable for months. Nothing has changed to the config, neither on the Edgerouter X nor in pfSense Also no firmware updates are installed or reboots happened.

What we tried to fix the connection:

• Restart Ubitquiti Edgerouter via UNMS (centralized management tool)
• Hard restart by unplug the power and reconnect it
• Deleting the IPSec settings on the Edgerouter and re-configure IPsec on the edgerouter followed by a reboot as it still didn't work.
• Reconfiguring the IPSec connection in pfSense (No reboot yet as this will pull down our whole network.

For now we have around 3 "broken" connections of the 30-35 connections. Whats the cause and how can i solve this? We need reliable VPN connections and if they are disconnected for really short period that they at least need to reconnect automatically!

Ubiquiti Edgerouter-X config: Offcourse the pfSense config is corresponding with the config bellow as the connection worked.

 ipsec {
     allow-access-to-local-interface enable
     auto-firewall-nat-exclude enable
     esp-group FOO0 {
         compression disable
         lifetime 3600
         mode tunnel
         pfs enable
         proposal 1 {
             encryption aes128
             hash sha256
         }
         proposal 2 {
             encryption aes128
             hash sha256
         }
     }
     ike-group FOO0 {
         ikev2-reauth no
         key-exchange ikev2
         lifetime 28800
         proposal 1 {
             dh-group 14
             encryption aes128
             hash sha256
         }
         proposal 2 {
             dh-group 14
             encryption aes128
             hash sha256
         }
     }
     site-to-site {
         peer ipsec.company.de {
             authentication {
                 id an_id_here
                 mode pre-shared-secret
                 pre-shared-secret Some_key_h3r3
             }
             connection-type initiate
             default-esp-group FOO0
             description IPSec_connection
             ike-group FOO0
             ikev2-reauth inherit
             local-address any
             tunnel 1 {
                 allow-nat-networks disable
                 allow-public-networks disable
                 esp-group FOO0
                 local {
                     prefix 10.130.3.0/24
                 }
                 remote {
                     prefix 10.128.0.0/16
                 }
             }
         }
     }
 }

screenshot pfSense config:

UPDATE: All our Edgerouters are connected to our UNMS server and by coincidence i restored a backup (made automatically by UNMS) and the IPSec connection worked again. I tried this at 2 different (ER-X) devices with the same IPSec issue and it solved the "broken" IPSec connection issue at bot devices. The strange thing is that I'm 100% sure that no manual changes are made on both devices between the date of the backup and the time the connection broke. This let met think that there is a bug in EdgeOS somewhere??