Server Version#: 1.15.6.1079
Player Version#: latest on LG as of 2019-5-29
I forgot to keep my old thread alive. So reposting. LG TV + Sonos + 4k file is still an issue. The only work around is to downgrade to 1080p.
https://forums.plex.tv/t/lg-webos-hdr-colour-glitch/296965
https://forums.plex.tv/t/lg-webos-4-0-1-15234-plex-app-3-64-2-4k-hevc-h-265-video-whitescreen-black-box-in-corner-issue/296490