Comment # 5 on bug 1124857 from Philipp Seiler

Unfortunately I'm using a Intel HD 5500 and used a Intel HD 4000 before.
The error was present in both hardware configurations.

I have this error since Leap 42.x (don't remember it exactly).
I haven't tried 15.2 yet, but I doubt that this is fixed there.
Some application won't get launched before I delete local .Xauthority and
restart the xdm.service afterwards.

This issue is really odd to me. I Still haven't found the real source for it.
My best guess still is lightdm in some way.