I don't know if this will work for everyone, but I was able to find a workaround that I can live with. I habitually use the "Close [Window]" [X] in the upper right, but instead, I added the "Save & Close" shortcut to my custom ribbon.
File --> Options --> Customize Ribbon (or "Customize Quick Access Toolbar", if you prefer) --> Choose Commands from: "All commands" (dropdown)
Select "Save & Close" and place according to your preference. I use the "Save as", "Undo", and "Redo" shortcuts, and wedge it in there.
When opening an appointment, instead of clicking the "Close Window" option, use the "Save & Close" shortcut.
Again, it doesn't solve the root problem, but I found that I could live with this.