Random disconnections on IPSEC VPN

[giulionet]

Hi everyone,
I'm experiencing an odd behaviour with an IPSEC VPN between two pfSense 2.4.4 nodes.
Once a day on average, the connection goes down for 10 minutes, prompting "no matching CHILD SA config found" in the IPSEC logs (image below). This is really driving me nuts since Phase 2 for the tunnel is definitely configured on both ends, and since the same configuration (of course different IPs and PSK) is working without a hitch on another infrastructure.
When I hit the "Disconnect" button for Child SA in the Status page, a new one is created and the connection immediately comes alive again.

Any help appreciated
Thanks