Since I upgrades from Ubuntu 19.04 to 19.10 I have a curious behavior.
When a dialog window opens, the main window shows its previous state (like the undo button was selected)? Once the dialog window is closed, the main window get back to its normal state. I see that behavior in different applications.
An example would be in LibreOffice Calc, I select a cell to change its format, When the cell formatting dialog box opens, the main spreadsheet shows its state as it was before the last action, as if the undo button was used. Once the cell formatting is done and the dialog box closed, the main spreadsheet get back to its normal values.

Not really a life threatening problem but still very curious.