I previously posted a topic regarding the SlingPlayer freezing up over-and-over again when running it on an Amazon Fire Stick with lots of network bandwidth. I was unable to post a reply to that topic but I think I have found the solution.
I don't think that the Fire Stick has enough horsepower to handle the video processing required by the SlingPlayer app. I replaced the Fire Stick with a Roku 2 box and it works great! One of the downsides of running SlingPlayer on Roku is that it requires an iOS device (iPhone or iPad) to run with it. That actually works very well. I use an iPad and I can use the iPad as a sophisticated remote control device (It shows a graphical depiction of my actual Verizon FIOS remote control device and works the same way. In contrast, running the SlingPlayer on the Fire Stick is much more confusing to find the menu selections you want.