I accidentally opened this file - and thought Designer had crashed. Spinner and an unusual long waiting time. There is no way to see that it is a brush file from the desktop icon (same icon for brushes and documents, not good), but fortunately I checked the file extension elsewhere and understood something could be happening under the hood. Designer didn't offer a clue other than Windows adding "Not responding" and the fan running faster for quite some time.
It was duplicat brushes so when the never ending proces ended - I removed the brushes again. Had to wait even longer. Still no feedback.
Some user will terminate Designer one day believing it has crashes - in the middle of the update. Doesn't sound safe.
UX solution: Designer showing a dialog with "Installing brushes, removing brushes, doing some maintenance" etc. Feedback.
Affinity_Airbrush.afbrushes