Here is an odd one i'm hoping someone can help with!

The system is a 7100 across two sites, site one has the system and has no issues, site 2 has around 6 phones and is connected via a VPN, the problem is site 2 is having issue where some calls have no speech this includes internal calls on site 2 where RTP traffic goes phone to phone, it not every call it can be 1 in 10 calls but then have 4 in a row. I have removed the switch from the firewall and used a different switch with just 2 phones plugged in and the fault was still there the firewalls have been changed each end to a different make with no change.

Can't be a NAT issue as it's happening on internal calls!

Any help is appreciated.

Thanks