Latest Sourcetree cannot always be redisplayed by clicking its taskbar entry.

On Windows 10, the latest version of Sourcetree cannot always be restored by clicking its entry on the taskbar.  The click appears to be simply ignored.

The workaround is to right-click the Souretree entry, close its window and then reopen the whole application.  Mysteriously, when I do this, it seems to have forgotten its previous window size and position and reverts to its defaults.