I have been having lots of issues with my 4k Sticks. I keep getting frozen with the spinning icon. Then it goes and a few minutes later it does again.
Never had this issue before.
Has your network changed at all? It could a network issue, and the devices are now using the 2.4GHz network instead of a faster 5GHz network.
If not that, has anything else changed? Software updates, new hardware, different settings?
Nothing that I can think of.. how can I tell if it's on 2.4 or 5?
It depends on your router/AP. There are too many different models and management interfaces to know.
Are you having problems with live playback, or recordings? If live, is Tuner Sharing on? Are you using OTA sources from an HDHomeRun tuner, or are you using streaming sources (Locast/TVE)? What does a speedtest from the Fire TV Stick to the DVR server show?