Internal routing

I know this is a basic question but I want to make sure I have this right before digging deeper.

At a site I have an Untangle Box:

eth0 ADSL Internet
eth1 LAN 192.168.0.1/24 < ---->main LAN
eth2 LAN 192.168.1.1/24 <---->internal router(192.168.1.2/24)<---->internal subnet(192.168.5.0/24)

The eth2 LAN interface doesn't have any of the NAT options selected i.e "is WAN interface", "NAT Traffic exiting this interface" etc.
I have configured a static route in the Untangle for the 192.168.0.5/24 subnet with the next hop as 192.168.1.2/24(interface of the internal router).

All PC and server connections between the 192.168.0.0/24 subnet and the 192.168.5.0/24 subnet seem to be working as expected, but a VOIP phone system won't connect between subnets.

Before I go into further troubleshooting of the phone system, am I right in assuming that with the configuration above it should be straight up routing between both subnets, no NAT and no packet filtering (unless I add rules)?
All traffic should be unmolested by the Untangle box?
The phone system uses diffserv QOS, but even though the Untangle may not respect the QOS it will still route the packets ok?

TIA