5ghz Issue

Xfinity did some upgrades in our neighborhood several months ago and I'm having disconnecting issues since then, especially the 5ghz wifi.

A few times a day, my iPhone, which is connected to 5ghz wifi drops internet connection. Looking at the wifi connection, it says it's connected but I have no internet.

If I switch to 2.4ghz, everything is working again.

I have the 200 Mbps plan and sitting right next to the modem (Netgear C6300), I get 235 Mbps on 5ghz while I only get about 40-70 Mbps on 2.4ghz. I guess this is normal?

Watching Netflix on my Samsung TV, which is also connected to 5ghz wifi, I get the spinning loading sign several times a day. After 5-10 minutes, the connection is restored on its own.

I wasn't having any of these issues BEFORE the UPGRADE and on a slower 100 Mbps plan. So it's really frustrating. 

I've changed the channel on 5ghz wifi and it didn't help. The event log doesn't show any errors even after I've had these disconnects on my iPhone or my TV.

Any suggestions?