Since my last post, I had emailed Asus support and they sent me a beta BIOS (took two weeks) which solved my problem.

I currently have version 1610 installed and haven't had any problems yet.

Since it's pretty much impossible to downgrade the BIOS on this board, don't install the latest BIOS version as soon as it's released, rather wait a while and be 1-2 BIOS updates behind. That way if you update to a new BIOS that's wonky, you can still save yourself by flashing the board to a newer BIOS (i.e. I've currently got 1610 on my board, I'll only update to 1702 when a new version is released (let's say 1800), that way if 1702 starts acting up I could easily update to version 1800 to try and solve the problem)

Try flashing your board to 1207 (IMO the best BIOS, 1307 had a tiny bit extra OC features though) then go up from there if you're experiencing any problems.