Changing keyboard layout with Alt+Tab broken lately

[Wise Ferret]

Up until today I was able to change my keyboard input layout with Alt+Tab (this cannot be set in the regular keyboard shortcut definitions, but is achievavle with gnome-tweak-tool).
This stopped working today. The Alt+Tab checkpoint is still marked in gnome-tweak-tool, but it does not work any more.
Any ideas?

EDIT: Solved with today's update to gnome-daemon-settings. However, gtk3 theme support is now broken and choosing a theme in gnome-tweak does nothing.