Yes, I have experimented this bug too, probably a bug into XFCE4 with the new docklike function for pinned apps (missings or removed after the pinned action)....
3.1. At that point minimizing through clicking on the active symbol will also not work anymore.
Maybe a workaround already exits to cancel/kill this old pinned app icon ?
@SwampRabbit
... Good news.Thanks for sharing the info on yad-calendar. I can look at it more later, we’ll see what we can do, the replacement for orage was pretty high on the list of things.