I appreciate this is ultimately a Kodi/add-on problem, so not looking for an OSMC solution, but it may have identified a problem for OSMC.
TL;DR Youtube add-on freezes OSMC when trying to play a trailer. Powercycle to clear.
The Kodi Youtube add-on home page allows you to play movie trailers direct from the information page of a particular movie. The trailer URL is scraped at the same time as movie details are scraped.
For the addon to run correctly (for trailers), you need to register with Google API and services, and type ID’s into the plugin. Google recently made changes necessitating (most users) regenerating ID’s. However, until those changes are made, it presents to the User as an ‘Info Page’ when trying to watch trailers: ‘The following content is not available on this App. Watch this content on the latest version of YouTube’. On OSMC, this screen causes OSMC to freeze (or flicker to a plain black screen) and drop off the network. OSMC is then unresponsive to OSMC remote and CEC. A powercycle seeems to be the only way to regain control.
