IPSec from pfSense 2.2.4 to Fortigate (don't know the version) flakey

[almabes]

I need help.

I have a client that has IPSec configured.  One has a pfSense 2.2.4 box running on a NetGate ADI 2440 box.  Single WAN.  I have IPSec configured and mostly working L2L connected to a fortigate firewall managed by a third party.

Site A
192.168.2.0/24 (pfSense)

Site B
10.100.117.0/24

IPSec phase 1 is configured to use mutual PSK, IKEv2, 3DES, SHA1, DH group 5.  Both ends match.

The tunnels come up and I can ping from the pfSense side to a host in site B, and everything is working.  People in site B can access what they need in site A.  However, periodically, and I have not discovered what defines this periodicity, traffic from site B does not make it to the IPSec interface on pfSense.  But if I ping my host in site B from site A, it responds like it should and traffic starts flowing again from site B.

This is maddening.  I need suggestions, please.
Thanks in Advance

[almabes]

Wow…nobody?!

[awebster]

Check your phase 1 and phase 2 lifetimes, sounds like there is a mismatch.