Error trying using regionset despite enough vendor resets available

I’ve got a new PC where the DVD region is set to ‘4’ and regionset gives me an error when trying to set it to ‘2’ even though it says I have 4 vendor resets available.

adam@gondolin:~$   sudo regionset /dev/sr0 regionset version 0.1 -- reads/sets region code on DVD drives Current Region Code settings: RPC Phase: II type: SET vendor resets available: 4 user controlled changes resets available: 4 drive plays discs from region(s): 4, mask=0xF7  Would you like to change the region setting of your drive? [y/n]:y Enter the new region number for your drive [1..8]:2 New mask: 0xFFFFFFFD, correct? [y/n]:y ERROR: Region code could not be set! adam@gondolin:~$    

This is the info from the hardware with smartmontools:

adam@gondolin:~$   sudo smartctl -i /dev/sr0 smartctl 6.6 2016-05-31 r4324 [x86_64-linux-4.15.0-54-generic] (local build) Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org  === START OF INFORMATION SECTION === Vendor:               HL-DT-ST Product:              DVD+-RW GA31N Revision:             A102 User Capacity:        730,214,400 bytes [730 MB] Logical block size:   2048 bytes >> Terminate command early due to bad response to IEC mode page A mandatory SMART command failed: exiting. To continue, add one or more '-T permissive' options. adam@gondolin:~$    

I don’t like that error!

I figure it might just be something to do with the fact that it’s a DVD drive and not a normal hard drive.

There’s currently a CD in the drive – it won’t accept a DVD and therefore regionset won’t run with a DVD, but according to regionset docs, that should be irrelevant.

This is Ubuntu 18.04 Bionic, from the server install where I then installed Xwfm4 on top, if that makes any difference.

Is the DVD drive some sort of Chinese no-name that will only work in Windows or something? Do I need a new one or is there some linux wizardry I can do?