Hi Martin!
I've done some testing related to YouTube Live, and the only application I've got that that I've been able to use to play YouTube Live continuously is SeaMonkey v2.35 B7 with the Flash 0.4.1 GA plug-In installed. Was watching LIVE a Memorial service for a late premier of Alberta who died tragically in a plane crash two weeks ago, for about 3/4 of an hour this morning, no problems.
For the other alternatives:
Firefox 38.8.0 does not work without Flash installed (get "your browser does not recognize any of the current video formats available"
(It is unclear as to how to install Flash in the OS/2 version - would be more than happy to test, if someone can let me know how to do it, as it does not seem to recognize the Flash installed, just an "OpenH264 codec"?)
SMPlayer 16.8.0 gives the same experience as Neil indicated - I need to use "kai (dart) mode under AUDIO for sound, even though I am using Uniaud on the partition, and typically use kva (Fast) for VIDEO. I also tried increasing the "Cache for Streams" under PERFORMANCE but it didn't help. You have to fully put in the complete URL for the specific live stream you want to view, to get SMplayer to find it (ie can't just go to YouTube Live and choose a video, at least as I've found
VLC/2 v2.2.4 has been wonky since installation with just videos, hard locking the system sometimes after playing them. requiring reboot so I've never had much luck with it - and don't think it would be any different for live streams.
Just my two cents worth - I was going to have a look on the SMplayer site, to see if they've encounter the "5 second rule" for live streaming. on other systems, and if there is a work around.
Best, Sir!
Mark