This seems to be pretty common on the web, but I did not found a solution.
Last week I did a clean install, theming and plymouth removing, as always.
Then I did not restart for some days, till 4.8 release.
This happens after lightdm login: background goes grey and panel empty with themed mouse, for about 10" (before it took almost 2").
Sometimes bg stays on login screen image, panel partially loads and mouse does not get its theme.
After this slow login, it runs smoothly.
Has anyone else ever experienced grey screen freeze between lightdm login and xfce session?