How to send VPN traffic via gateway? Static routes & Firewall rules are ignored

[dims]

I am trying to connect to some OpenVPN server with OpenVPN client from LAN machine behind the pfSense router.

Experimentally I found that my server restarts connection if multiple WANs are enabled.

Now I am trying to do so that it worked with one WAN automatically, i.e. I want to pass all UDP traffic to specific address via specific interface.

I tried:

1. add firewall rule with IP + UDP + gateway ==> didn't worked

2. add static route with IP ==> didn't worked

3. add top firewall route with IP+UDP and w/o gateway to trigger default routing usage and + static route IP ==> didn't worked.

I am observing interfaces with tcpdump -i IFACE host HOST.

I started OpenVPN connection from Windows machine and started ping -t 10.10.0.62 where this IP is from VPN subnet.

In any case I see most packets go through single WAN interface but some packets still go through another WANs.

Why? How to force UDP traffic to go via specific gateway correctly?

[dims]

It was idle OpenVPN connection from third machine from the LAN keeping tunnel and packets going!!