Sounds like bandwidth issues to me. Usually the bandwidth from a residential internet connection is geared towards downloading of data. For uploading only a fraction of that is available to you.
Furthermore, video requires very consistent upload capabilities and residential connections aren't usually not optimized for that. That is where very different priced business connections come in.
Also, making sacrifices in video resolution will improve playback speeds. Downgrading resolution will show you the capabilities of your connection.
Getting a business connection is not a guarantee either. You can optimize all you can on your end, but if your ISP doesn't (too much overbooking, software settings and/or hardware) it is still in vain. Besides that, your telecom provider might also throttle bandwidth if you are in a place where the ratio of phones and antenna's isn't optimal. And with big businesses paying your (telecom) provider to get priority on bandwidth...
There are so many points of failure in getting local hosted, high quality video to work, especially on phones. The only place where watching a locally hosted video through a browser on a phone is on your own local WiFi network...but then you might as well watch it on a monitor.