"An unexpected error occurred…" Airport devices

Airport devices, from the Express to the Extreme to the Time Capsule, don't work nice with me. I've had to resort to alternative routers (Ausus) to get wi-fi working. But I prefer Apple, when it properly functions.

I've done scores of resets, including factory, but still get the same message: "An unexpected error occurred. Try again." This has happened too many times over the years to count; an experience I have not encountered with the Ausus. Perhaps someone can assist. I'll offer details below.

After a reset, I attempt to configure the TC (or other Airport device) using my iPad. The TC (latest generation) is recognized in Airport Setup, which is "gathering information about (my) network," as it is "joining Airport Time Capsule." The gears go round and round. After a minute or so, the error message is generated. All this time the TC is blinking amber. I try again and again and again. The definition of insanity. So I put my devices back in the closet. (Note: Every once in a while the device will allow me to "create a new network," in which case I put in a new name then plug in the Ethernet cable to the WAN port as directed. However, the device eventually stops functioning, though I have a solid green light.)

Of course, the units beckon from beyond. So I occasionally retrieve the devices, then go through the routine again. I reset. Same error message. Repeat.

I've been on the phone with Apple support. They are sympathetic, try to be helpful, but are ultimately bewildered by the repeated error messages. Typical with support, they suggest that the device is broken and that I should schedule an appointment with a Genius. But surely not all of the devices (two Expresses, an Extreme, and the Time Capsule--all latest generation) can be simultaneously broken. I suspect something else is afoot, yet have no idea.

I have Gigabit broadband via Ethernet (the apartment is wired so). The service is now connected, via a Gigabit Ethernet hub, with the Ausus router and my iMac, which runs the latest version of Yosemite. The iPad Air runs the latest iOS as does my iPhone 6.

I will put the Airport devices back into the closet for another day, then retrieve them again if someone has a solution.

Thanks.