v1.22.1.4200 has some issues on ARM v7 based systems right now, and the devs are investigating. Try reverting back to the previous version. You can download the “last stable version” v1.22.0.4163 by turning “Plex Pass Downloads” off from the download section.
You can also try the preview version v1.22.1.4204 from Plex Media Server - Forum Preview: Faster and smaller builds with new toolchain! . This one works for my QNAP TS-831X, but apparently not for everyone.
