Why do I need to play a DVD in VLC to make it "openable"

[bvrulez]

I experience that MakeMKV fails to open DVDs. I have to play them in VLC, first. Then, after they have been played once, MakeMKV can open them without failure. I have two PCs running Ubuntu 16.04 and I only experience this on one of them. I remember to have been reading something about it and maybe found a solution for an "automatic opening" already, but I forgot. Can anybody relate to this question? Thanks! Ben