In fact there are 2 devices for each drive: one /dev/srX and one /dev/srY. Both usually need to be mapped. You can use the container log to see if you have correctly mapped the drives:
[cont-init ] 54-check-optical-drive.sh: looking for usable optical drives...
[cont-init ] 54-check-optical-drive.sh: found optical drive [/dev/sr0, /dev/sg3], but it is not usable because:
[cont-init ] 54-check-optical-drive.sh: --> the host device /dev/sg3 is not exposed to the container.
[cont-init ] 54-check-optical-drive.sh: found optical drive [/dev/sr1, /dev/sg4], group 19.
[cont-init ] 54-check-optical-drive.sh: WARNING: for best performance, the host device /dev/sr1 needs to be exposed to the container.
So in you case, one container should have:
/dev/sr0
/dev/sg3
And the other should have:
/dev/sr1
/dev/sg4
The new image is already available