I recently just re-flashed my Linksys WRT1900AC v1 from DD-WRT to OpenWrt. I was able to setup the router properly in client mode connected to a WiFi connection (I call it the WWAN from now on). I already change the default IP to 192.168.2.1 so it doesn't interfere with the main WiFi. I also have setup a fixed IP to the WWAN and for most of the time, it works fine and I can connect to internet through the router ethernet or the WiFi re-broadcast. WWAN is in 2.4GHz and the WiFi re-broadcast is only in 5GHz.
However, every so often, the WWAN connection appears to slow down to 2Mbits and internet will stop, despite the fact that the router is still connected to WWAN. This seems to happen more often if I downloading something big (> 2GB). The temporary solution is to restart the 2.4GHz radio. It usually works after that but soemtimes, a full power cycle in required. This issue has been bothering me a lot since it also seems to happened when ever I was in the middle of video call.
I have set beacon interval to 50 and DTIM interval to 1, which seems to reduce the time sit happened but not fix it permanently. Any suggestion on what i can do to eliminate this issue?
Edit: I am running firmware version OpenWrt 22.03.0 r19685-512e76967f / LuCI openwrt-22.03 branch git-22.245.77528-487e58a