Got this issue after update also, I ended up changing to the "Official Plex Repository" https://rawgit.com/Squidly271/AppsThread/master/forumpost0.html
Copied URL and Repository Name details to the broken/same plex docker container and I was back up and running in minutes...
Repository:
plexinc/pms-docker
Docker Hub URL:
https://hub.docker.com/r/plexinc/pms-docker/
Icon URL:
https://raw.githubusercontent.com/plexinc/pms-docker/master/img/plex-server.png
WebUI:
http://[IP]:[PORT:32400]/web