Since a while the notification bubbles over the application icon in the dock do not disappear anymore. It started with the AppCenter a few weeks ago. Usually, when there are new updates, there was a notification and the bubble above the icon, but after updating the bubble disappeared. Now the bubble stays, even after updating everything. Since a few days I have the same problem with Thunderbird, the bubble stays even after reading all my new emails. After restarting the bubble disappears, but that's not really a long term solution.
Does anyone know why this is and how to fix it?