after some time traffic stops through tunnel

[boneyard]

a bit of a vague subject but is also a vague issue.

we got dozens of VPN tunnels from 100D / 100E (running 6.2.4 currently, but the issue also happened while on 6.0) to different VPN devices. on some of these it sometimes happens traffic doesn't flow correctly after some time, it enters the tunnel but doesn't return. the tunnel status is up (phase1 and phase2).

trouble shooting is a pain because the other side is managed by another company (different one per VPN) and calling, trying to get someone who can check and actually trouble shoot / debug takes too long.

so the solution is just to reset the tunnel, either via CLI or via GUI. then it works again. but that isn't really a solution you want to keep doing.

what can this be? we checked the settings (proposals, time outs, ...) those are identical.

has anyone been in this situation and actually solved it with a clear reason for it?