Dear Alex, It looks like "gtk3-engines-oxygen" is no longer compatible with GTK-3.4.
Could you please install "libgtk-3-0" from testing to check if it fix this problem for you? Thanks. Regards, Dmitry Smirnov GPG key : 4096R/53968D1B -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org