Using a RT-N12 C1 router and a desktop on a P8Z77-I Deluxe.

Desktop is having issues with packet loss causing lagspike and sometimes disconnects when gaming. This is despite the desktop being just one room away and Windows gives a full signal bar for the wireless network. Tested with LAN connection to check if Unifi is the issue, but that doesn't seem to be the case. Using 2.1.1.1.67 firmware on the router.

Any suggestions on how to fix this?