RT-68U Drops Internet when VPN activated

[keyboard99]

Hi

I have been using the RT-AC68U for a few months now as my home wireless router with the modem in a DMZ.

Recently I set up the OpenVPN side of the router so all my devices would router via my VPN. OK I notice a drop in speed (using PC Win 7)as you would expect with a VPN the internet speed halves. Once VPN is enabled on the router the internet works for a while but then I get complete drop outs in usage, web browers report page failures and my samsung phone drops the wifi, it comes back again for no apparent reason, the VPN its still showing connected in the asus menus through all this.. As soon as I deactivate the VPN in the settings everything works a treat. I am running 378.56_2 and followed this tutorial https://vpntips.com/vpn-router-install/

System log has a lot of these

kernel: [truncated] L/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/npch ==NULL/np

rc_service: httpd 431:notify_rc stop_vpnclient1
Dec 11 15:30:13 openvpn[678]: event_wait : Interrupted system call (code=4)
Dec 11 15:30:15 dnsmasq[5859]: warning: interface ppp1* does not currently exist