12th December 2016, 13:24
I have finally found the rootcause of this. It was the modesetting driver. When I reverted back to the intel driver, the xembedsniproxy starts OK at startup again. So I guess modesetting is not ready for prime time yet. I've also noticed various glitches with modesetting in plasma, especially with turned on Informational tips, with window thumbnails on taskbar - they are sometimes corrupt.