And now, it looks like the fun is about to start. I moved my Fire Stick from my secondary TV (close to the wifi router) to my primary TV (further away from the router). The reason I did this is that my Apple TV, which used to be connected to my primary TV, really started acting up on wifi connection. Even very close to the router, Apple TV was buffering a lot, dropping video resolution down at the same time. It was going on for a few days, so I decided to try direct Ethernet connection, which is only close to my secondary TV. That works fine. But since now I had to move the Fire Stick to my primary TV (where Apple TV used to be), Fire Stick started experiencing wifi connection issues (never seen before, when it was closer to the router).
It is pretty weird. For example, yesterday it was running without a glitch, but today it wouldn't connect to anything ("no network connection" error) for a good few hours, and then it came back a few hours later, streaming everyting perfectly. I have been checking wifi signal strength in both cases, when it works and when it doesn't, and there hasn't been a significant difference, if any. Netspot app reports between -52 and -55 dBm, and everything else works fine. Boosting the wifi signal, with the addition of a wifi extender may (or may not) be the solution, but I'm trying not to waste any more money, because everything else is working fine, the way it is now. It appears that wifi is one of the main Fire Stick issues.