I have an issue that resurfaces from time to time, especially after AP is rebooted (because firmware updates, as I don't reboot them regularly).

There are multiple SSIDs with many VLANs and every single one of them is either set as 2.4G-only or 2.4G+5G. But once I create a network that's supposed to run only on 5GHz, I'm getting a headache, trying to force it to work.

Here, it doesn't matter if it was created some time ago (and AP has been rebooted) or it was added recently.

So, the SSID can pop up, but no device can connect to it. Sometimes the SSID disappears completely. Maybe it'll pop up back again, maybe it won't. There's no rule here.

One might try rebooting AP time after time, hoping it'll come up, will stay visible AND clients can connect to it. But there's no telling when it'll break again (it doesn't always stop working - yesterday I upgraded APs to 1.3.6 and all was fine, but once they've been updated to 1.3.7, thing stopped working again). On previous FW (1.1.1) issue was also present, but after some reboots it started working, so I ignored the issue for the time being.

Any and all issues stop, when I enable 2.4G for that SSID. Thing is, I want to have it as 5GHz for a reason and I want it to work reliably. Once you drop the 2.4G and leave only 5G, thing's broken again. It doesn't affect any other networks/SSIDs - everything else is working perfectly fine.

I'd be grateful if you guys could pinpoint what's the problem here. Is it my specific config, or it's a bug that needs fixing.