Am probably having the same problem, occasional 5 gigahertz slowdowns until a Merlin router reboot. However since Merlin does NOT write the code that directly operates the WiFi radios at a low level (it's Asus code), and Merlin is always going to use basically the latest Asus drivers in any Merlin release, there really is no point in telling Merlin about this kind of problem. I.e. Merlin is going to change the low level driver on a schedule that is not dependent on whether or not a few of us have occasional 5 gigahertz troubles.
The thing to do if you don't like current Merlin radio drivers is to wait for a new Merlin release, or change the firmware to (a) some earlier Merlin release or (b) DD-WRT or indeed stock Asus firmware (which is always going to have the very latest Asus drivers).