Is this still an issue for you or did you return it?

I am having similar issues with my c2300 where the 5ghz will just drop (when in "Smart connect" mode).

I have this same problem.

Every 1-2 weeks routher has problem wiht 5ghz connection. My phone have problem with authorization, next wifi disappears 

I have to restarting router or back to factory settings.

Please help

2.0.3 Build 20180810 Rel. 62903

@Flyersman I also have a similar issue with a three-day old C2300. Wifi network access spontaneously breaks after some hours. Android/iOS and Windows devices are unable to connect on either 2.4 or 5Ghz connections reporting 'authentication problems'. Reboot fixes it, until it breaks again.

I'd like some guidance on how to further diagnose the issue.

@Flyersman Having a similar issue with my TP-Link A2300 on the latest firmware, have had it for a little over a year. This started happening at the start of October when there were no issues previously.

5Ghz will be working fine, attaining max speeds for my ISP for a little bit then suddenly become unstable and then be unable to connect. This happens simultaiously across all devices connected to the 5Ghz. Waiting about 30 mins to 1 hour lets me reconnect and it takes about a few hours before connection stablizes.

2.4Ghz works fine through out the entire time.

What is going on here?

Same problem for me. Setup the router fine and now nothing can connect to 5ghz. I had 5ghz working for about 12hours after setup. I have rebooted, changed channels, security, everything.