We stumbled over a situation where the wan environment did not advertise lower mtu values properly or fragments where routed over a different path.
To FIX this we set the MTU / MSS values on the route.
vi /etc/network/st_routes
10.0.0.0/8 via 10.52.192.81 dev eth0 mtu 1150 advmss 1100
default metric 0 via 10.52.192.81
This is not possible via CLI on the Avocents.
