I'm having a rough time across the board with streaming.
For a while I've had a Mac mini hooked up to my tv running Plex. I would start by attempting to watch a show through the GB Plex plugin. This would often work, but if it wouldn't load or if the stream would keep stopping to buffer, I would quit Plex and open up safari or chrome to keep watching. If the stream would get caught in a buffer loop there, I'd do the trick of modifying my hosts file. Usually this would make things solid enough to get a couple of shows down. I'd go through some stretches where the Plex plugin would work flawlessly for weeks, then stretches where even changing the host file multiple times wouldn't avoid constant buffering.
The Mac mini started getting a bit long in the tooth, so I recently migrated to an AppleTV. I know the app there isn't official, but it runs me through the same loop only with much lower reliability against buffering. I usually start by trying to load a stream through the app. This straight up works maybe 10% of the time. Often it'll get about 2-4 minute into a show then hit a hard buffer loop where it stops, buffers for around 3 minutes to play the next 5 seconds. The rest of the time the stream either won't get past the first 5 seconds or won't load at all. When this happens, I'll usually open the site on my phone and fiddle around with AirPlay to get it playing on the tv. My success rate with that is much higher (despite the annoyance that it pretty much ties up my phone), but even so I'd wager at least half of the time it gets caught in short buffering loops (play 10 seconds, buffer 1 second), gets stuck in a low quality version of the stream, or locks up completely and won't buffer any further. Since I don't have the option of modifying the hosts with my phone or appletv, my last resort is to go unplug my modem and router for 5 minutes and try again. Add in the requisite note that the appletv is connected via ethernet, and I never have issues with HD streams from youtube, Netflix, or any other sources.
Pleease let me know if there's any additional info that would be helpful, or if there are any other tricks I should try. The constant dance to get things working has gotten pretty tiring.