OpenVPN client and LHGG LTE6 kit

Hello. I’m trying to configure OpenVPN client on LHGG LTE6 kit. It connects to the server (RB5009), but no traffic passes, no one route is working and connection drops every 50-90 seconds. Connnection status only shows activity on TX, while RX=0.
But if I configure the same OVPN settings on Mikrotik hAP connected to LHGG eth1 port, connection to the OVPN server is fully working and it is absolutely stable. Here is a brief diagram:

Diagram

I use almost default settings on LHGG and only configure ovpn client in PPP and port 1194 in the firewall.

Please advise the way to resolve the problem, a couple of threads on forum are related to the same without solution.

Thanks in advance for any suggestion.

Resolved!

After a month of fighting I have accidentally found very simple solution:

/ip route
add dst-address=<OpenVPN-server-IP>/32 gateway=lte1