IPSec Site to Site VPN working for days, suddenly no more traffic through tunnel
I'm using the latest pfSense 2.3.4_p1 and have about 50 IPSec Site to Site VPN connections. All tunnels work fine, but since a few months (new pfSense updates?) after a number of days all tunnels no longer send traffic anymore. As far as I can see they seem to receive traffic, but don't send traffic. The only workaround is to stop the VPN service, and after a few seconds start it again. Then all tunnels come up and traffic is passed again both ways.
Any suggestions? Is this a bug in the VPN server?