>Yes, there are multiple users, all have the same problem.
Are these users using different types of devices or are all the devices the same type?
I haven't seen it for a long time, but some devices don't process BSSIDs that well. BSSID is what is used to advertise "SSID"s 2 and up from an AP. An SSID is used for the wifi network.
If all the devices are the same type then it could be this issue (which is a device issue).