Mac Mini frequently loses connections (both Wi-Fi and Bluetooth) I have a Mid 2011 Mac Mini which is connected to:


Airport Express
Apple Bluetooth trackpad
Apple Bluetooth keyboard


Suspiciously frequently and quite consistently, maybe every other day, one of the three disconnects, and I have to reconnect them manually, which usually goes fine immediately.

For comparison, my MacBook Air never disconnects from the network. Battery health on the trackpad and keyboard does not seem related to the disconnects.

Since all three of the devices disconnect, the culprit would seem to be the Mini, particularly the Wi-Fi and Bluetooth adapter. But I don't want to jump to conclusions.


How can I best diagnose the situation to understand what is wrong?
Is it likely that replacing the Wi-Fi/Bluetooth adapter would resolve the problem?
Is it likely that replacing the Wi-Fi/Bluetooth adapter would resolve
  the problem?


Yes.

It's highly likely that the issue is the Airport card because it is a combo Bluetooth and Wi-Fi adapter.  Given that you are having issues with both functions, it points to the adapter being at fault.

You've already done a significant amount of diagnostics and ruled out other machines don't exhibit the symptoms connecting to the same network.  You can further verify that your Bluetooth peripherals are not the issue by connecting them (keyboard and trackpad) to the MacBook Air.  You could also run AHT - Apple Hardware Test.  It may detect a problem with the Airport card.