Traffic Blocked ramdomly

[Jules_L]

Hi,
I have installed OpnSense on Proxmox, and I have enable DHCP server, but I have an issue that I had with PfSense:
When I start a connection, everything is fine and then for mobile phone for example, when I stop using it and come back 5 minutes later, I ve got error timeout.
I can't access to local network too
It is the same on my computer.
But the DHCP leases are still active because I let the DHCP leases last 2 hours (default time)

When I get these error, I'm trying to ping IP Adresses and domain names such as 8.8.8.8 1.1.1.1 google.com and it fails.
Seems that the firewall is blocking traffic randomly

I've got a Double Nat Config and the WAN IP of OpnSense is in the DMZ of my isp box
Thank you for your help
Jules