DVD problem

[Richard Kimber]

When I insert a DVD I get a window saying words to the effect of
"Unable to mount disk it is already mounted"

I have set caja to do nothing for all media insertions, and never to
prompt on media insertion, and I have told it not to browse media when
inserted.

So what is (a) automatically mounting the disk (and how do I stop it?),
and (b) what is sending me the message that it can't mount the disk
(and how do I stop that)?

Basically, I'm just trying to use K3B to write an iso, but it always
fails with a write error, which I assume is related to the above. I
tried using the Disks program to restore an image, but it tells me that
the DVD is read only, presumably because something else has mounted it.

I'm using Ubuntu Mate 19.04

- Richard.
-- 
Richard Kimber