It says use it for non-GUI newest release upgrades? Why are you surprised the GUI disappeared?!

Also, why did to do that, if you wanted to keep the current version?

Anyhow, I never have such issues with Debian. Do bear in mind, Ubuntu(or any distro) is not Linux.

Are you going to call Linux "unstable", because you get a crappy phone with Android(which is judt more Linux).