The best I can tell, it seems that Plex is having an issue during content scanning as a nightly task and soaks up all the memory. Not sure what the hell is going on, but by adding a hard cap on the memory assigned to the container, I just get the OOM killer reaping the container rather than my entire box locking up. There really is no good reason for a non-privileged docker container to be able to effectively lock up the host operating system.
