Server Version#: 1.18.2.2058
Player Version#: Plex for Mac 1.4.0.924-60046db9, Plex Web 4.14.2
This issue started happening after upgrading to the latest version which fixed the tvdb metadata download issues. Now, the metadata downloads, and I can see the images when click edit on a season. When I select an image for a poster and save, the season poster becomes empty no matter which image I select.
I can reproduce this with any newly added show in this version of plex. Shows which I had in my library before the update work fine.
I have tried clearing the cache for tvdb, removing the show from library, empty trash, clean bundles, optimize database, adding the same show back. I can always reproduce it.

Logs
Nov 24, 2019 07:20:38.055 [0x7f43d6ffd700] ERROR - Error bringing media local (metadata://seasons/1/posters/com.plexapp.agents.thetvdb_63e4fa62cbd93426c32ae8b15632afc74c946e24).
Nov 24, 2019 07:20:38.278 [0x7f43d67fc700] ERROR - Unknown metadata type: folder