Is there any chance to make some kind of diagnostics for Airport Extreme (5th Generation).
It is exceedingly hard to get info out of the Extreme.. apple have very little diagnostics or logging even when you use a v5 airport utility I am pretty sure you are not going to see why a particular stream is having issues..
It would require low level look at the firmware.. and apple gives no way to access that.
How brave are you?? You can solder in a serial port and get console output.. how useful that will be I am not sure.. but you might pick up things like memory leaks, CPU overloads, etc.. however that doesn't fix it. In other words having output still gives you no way to repair what the issue is.
If you have not previously had issues and this is setup that has not changed.. let me at least suggest.. downgrading the airport firmware to 7.6.1 .. I find it a heck of a lot better for most of my usage.
In a v6 utility hold down the option key whilst you click the version number. Select the firmware from the list.. it will then downgrade.. you can also upgrade the same way so this is purely a test.
I would then recommend the following changes. Some of this is for Yosemite which is particularly problematic but it may help you as well.. if you upgraded anything to yosemite recently .. that could well be the cause of your problems. Point 5 below about using Link-local only for ipv6 is crucial.
Factory reset universal
Power off the AE.. ie pull the power cord or power off at the wall.. wait 10sec.. hold in the reset button.. be gentle.. power on again still holding in reset.. and keep holding it in for another 10sec. You may need some help as it is hard to both hold in reset and apply power. It will show success by rapidly blinking the front led. Release the reset.. and wait a couple of min for the AE to reset and come back with factory settings. If the front LED doesn’t blink rapidly you missed it and simply try again. The reset is fairly fragile in these.. press it so you feel it just click and no more.. I have seen people bend the lever or even break it. I use a toothpick as tool.
Then redo the setup from the computer with Yosemite.
1. Use very short names.. NOT APPLE RECOMMENDED names. No spaces and pure alphanumerics.
eg AEgen5 and AEwifi for basestation and wireless respectively.
Even better if the issue is more wireless use AE24ghz and AE5ghz with fixed channels as this also seems to help stop the nonsense.
2. Use all passwords that also comply but can be a bit longer. ie 8-20 characters mixed case and numbers.. no non-alphanumerics.
3. Ensure the AE always takes the same IP address.. this is not a problem for you as the cable modem SB5102 has no router.
4. Check your share name on the computer is not changing.. make sure it also complies with the above.. short no spaces and pure alphanumeric..
5. Make sure IPv6 is set to link-local only in the computer. For example wireless open the network preferences, wireless and advanced / TCP/IP.. and fix the IPv6. to link-local only.