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:

add firewall rule with IP + UDP + gateway ==> didn't worked
add static route with IP ==> didn't worked
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!!