yes i too have had the problems with plex you have mentioned after installing v677, however i have also updated the plex media software on my computer which seems to have resolved most of the issues with the exception of sometimes not being able to play some of my 4k HDR/DV video files, not sure why, but have found restarting the tv will rectify it temporarily.On V677 (ATV 11 55C715) the plex client seems to have some repeated crashes, doesn't store last played, sometimes wont start from beginning or resume properly. Has anyone else experienced this? I have updated the Plex client to the latest version from the app store but this didn't fix the issues either.
I also have an issue where from "Home" screen launching BBC iPlayer asks me to accept the Freeview Play T&C's but there is no way to accept them. Under the advanced settings menu they are already accepted (and i have tried toggling them, restarting and accepting them again). Launching iPlayer from the Freeview App works fine and the app launches fine from the TV guide as well when "catching up" on TV shows.