I’ve also observed this behavior. Save yourselves some time and just make a bash script:
plex.sh:
#!/bin/sh
wget "https://plex.tv/downloads/latest/5?channel=16&build=linux-x86_64&distro=debian&X-Plex-Token=XXXXXXXXXXXXXXXXXXXX" -O plex.deb
sudo dpkg -i plex.deb
rm plex.deb
exit
