Keeping devices connected via wifi bridge / repeater continously connected to main router?

I recently set-up a TL-WDR4300 with OpenWRT to use as basically a bridge. I set up luci-proto-relay to bridge connections and it works fine. All DHCP requests anything is forwarded STRAIGHT to the main router.

I hooked up a PC in that room to the new router. Now the problem is, what seems to happen is the PC only contacts main router when it needs to, it isnt continously connected like in a LAN. I want to be able to access the PC's contents like as if it were in LAN. What I've done for now is set up a keepalive script which pings main router to keep that connection alive, but this isnt a solution im proud of.

Is there anyway to keep devices on the wifi connection of the repeater router continously connected or be in the LAN of the main router? If not, can I access the LAN of the repeater router via another method?