I just recently had an issue with my 3200ACM router. It had been running on LEDE/OpenWRT pretty much since I got it about a year and a half ago. There were a few issues at first, but as updates came, the problems went away until a couple weeks ago. When I am on OpenWRT, I no longer have access to the 5GHz network. It shows as active and available, but when I try to connect from any device (multiple computers and phones), nothing will connect. In Luci, it shows as "Wireless is not associated". I tried multiple settings as well as auto with no change, and also reset to original OpenWRT settings without success. As a final resort, I switched back to the factory firmware, and low and behold, everything is working again.
I didn't have time to try going back to OpenWRT until today due to the holidays, and the same issue is coming back again on OpenWRT. I was on the latest OpenWRT image and all packages, including the WiFi driver, were up to date. I switched back to the factory firmware again just so I have both networks again, but can go back to OpenWRT for testing to get more information if people can help figure out what is going on. It just seems odd to me that it works fine on the factory firmware, but not OpenWRT, and also that it is only affecting the 5GHz wireless and not both. Any help would be appreciated as my initial checks did not show anything.