A Strange, Unsolved WLAN Problem

I’m seeing strange behavior on the WLAN at one location. This location is one of many that are on the same controller and identically configured, save for AP locations and IP addresses. No other site is reporting this problem. Here’s my problem description:

Users report that many devices are unable to access “any site that requires a login”. From what I’ve seen, this really means most (but not all) SSL protected URLs. HTTP URLs work fine, HTTPS URLs timeout. This only happens on the open guest SSID. If one connects to the secured corporate SSID, everything works normally. Reports indicate that many, but not all devices are impacted. We couldn’t find a single Apple device that was impacted, but on-site staff believes it hits some of them, too. One of the staff owns an Android phone on which the problem is reproducible. I’m heading out there tomorrow with a suite of test devices to see if I can duplicate it with any of them. There is a possibility it only hits 802.11ac devices, but this is not the only 802.11ac site and it is the only one reporting this problem. I have connected with an 802.11ac laptop and had no issues. The 2.4GHz RF environment leaves something to be desired (and was the source of the Spectrum Analysis as Art post), but this problem also occurs on 5GHz. The APs are in FlexConnect mode, so I tried switching them to local mode and that did not change the behavior.

Does this sound like anything someone has seen? Any ideas what is going on?

FIN