> looks like you try to mount empty disk that has not registered in udisks2
The dvdr has data on it.

> can you mount from the command line?
only as root and I need to specify a mount point.
the other doesn't need root or a mount point.

> does same disk mounts in the other device?
Yes.

> do all disks in sr1 not mount? you mention specific as user
Yes.

If I reverse the order.
For example, turn on optical drive "a" second, make it "b" (sr1), it exhibits 
the same behavior (can't mount). 

sr0, always works as expected. sr1 doesn't.

Kate