After upgrading to Ubuntu 19.04, I have noticed a visible freeze of a couple of seconds whenever I click a button of a Gnome dialog window. One case when it appears is the screen unlock window, but even the "open file" dialog in most applications gives the same behaviour.
Journalctl displays some error messages that appear to be related [EDIT: the messages were a red herring apparently; they do not appear at the same time as the bug happens.]
Any ideas as to what could be causing it? Is it a known problem? Any experiment