2.4Ghz fine while 5Ghz randomly drops saying "Connected, No Internet"

Hi, I've been having WiFi issues for months, and have been struggling to diagnose what the cause could be. I've gone through several different pieces of equipment, and have begun narrowing down what the symptom is, but I have no clue how to fix it. I would appreciate any/all help on this.

For several months I had been noticing frequent inconsistent disconnects from the internet. Usually would notice my phone saying "connected, no internet", and my laptop would drop and reconnect as well. At this time, I was using Google Nest WiFi, which doesn't let you choose between 2.4 and 5Ghz.

Since then I have changed equipment around a few times. I am now on a Netgear Nighthawk Modem/Router. I've kept the 2.4 and 5Ghz bands separate, and have noticed the issue seems to be only happening with 5Ghz. I've used netspot to make sure the 5Ghz is running on uncongested channels for my neighborhood. To me, this implies there is some sort of 5Ghz interference happening, but if that is the case - why would my devices be able to stay connected to the router as "connected, no internet"?

I've begun hard wiring devices I can that are close to the modem/router, and have not noticed any drops on anything hard wired the entire time I've had the issue. However when my TV was previously on the wifi, I would notice it would experience the issue even though it was right next to the router (it would sometimes drop a stream, but usually I could just tell it would go back and forth between very low and very high resolution).

I'm paying for 300Mbps down and normally get around that.

I'm normally tech savvy, but so confused by this issue, and have no clue how to resolve it. Any help would be very much appreciated!