I have the same problem. Used to work fine, and trailers still work fine on other devices such as web browser or Android app. I assume there must be settings in the TV that have been screwed up oh, but I can’t find it. I do miss them.
Same issue here. I really don’t want pre-roll trailers but I like to occasionally watch trailers manually when picking a movie, and it loads a black screen and playback controls but it stays black for the length of the trailer with no audio. Most recent Webos and updated plex server today.