WiFi switches from AC to N randomly

I have a Broadcom BCM94360CD which will randomly switch from AC (5ghz) to N (2.4ghz) and slow me down, sometimes even cut out the internet totally. No idea why this happens or what triggers it. The only way to "fix" it is to turn off and on the wifi, and everything goes back to normal until it switches again.

Not sure when this started, but I've been noticing it more and more the last few weeks.

Anyone have any ideas? I've done research and found nothing.