As the title says, this is what I'm dealing with. There is a vpn in place for this and the routers used are Sonicwall TZ100's. Apparently intercom calls between the two sites drop after 15 minutes. Panasonic support says there is some kind of tcp/udp timeout option that needs to be turned off. I don't have access to Sonicwall support so I don't know what to tell my customer to look for.

Anyone ever deal with this?

Make sure the trunk group the gateway is in cos 1 and in trunk group settings the co to co limit is disabled. Default time is 10 min

Timers have been checked and disabled where necessary, but I don't remember if the group is in COS 1. Does it need to be in 1?

it will only affect some numbers being dialled through gateway

you can run a trace in utility to see what's happening or put the maintenance port in to mirror mode and run wireshark