pfSense issue - network timeout?

I'm running pfSense in a KVM and a PBX server in another KVM.
I connect through a VPN to the pfSense server, all is working fine, now I can ping my pbx server "behind" it, the only issue is I get timeouts every few pings.

Normally one would blame this one the NIC, but as these are virtual NIC's and there is no problem with the host's NIC.
What could be the issue ?
 

About

The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!