Since a few days my Gnome desktop (v. 3.28.4) is showing notifications that appear only for a fraction of a second. I manage to see the notification bubble and that it contains some text, but I have no chance reading the text in it before it disappears.
I've tried to run
dbus-monitor "eavesdrop=true,interface='org.freedesktop.Notifications'", but it doesn't print anything for these ghost notifications. Some notifications (e.g. from Slack) work fine, and also get printed correctly by the above command. So I'm not sure if these ghost notifications even come through dbus.
My question is, how can I debug this? How can I find out which application / service is sending the notifications? Does Gnome write a log file that I could check? Or can I enable some kind of debug logging? I've also tried an extension that should keep notifications listed until they get dismissed, but that didn't change anything. Perhaps there are other extensions that can help here?