Try holding down the power and the volume down buttons at the same time for around 10 seconds, then the device should restart and run normally again.
I remember with a situation with my iPhone when it got frozen and I had to reboot it with the same approach. This also worked on my Android phone which was stuck on 0% firmware update.
This is a really old question but I have an answer for anyone wondering.If you do not care about playing DRM-protected content, just replace /system/bin/drmserver with an executable file that does nothing (e.g. just sleeps forever). Example: File someone made for a Magisk module that disabled DRM