Moving the Monitor panel around and resizing it causes other panel titles to be hidden. See attached 'titles of panels below are hidden from view 1.png' (please ignore the highlighted square box in the middle, it's there by accident) and 'titles of panels below are hidden from view 2.png'.
Preview monitor size settings are not retained when R6 is restarted (although the titles of other panels are then correctly shown). See attached 'after restart.png'. Unfortunately, I made the screenshot after resizing, so it doesn't show this and I'm too lazy to redo

, but when R6 is restarted, the Preview Monitor is a lot smaller than the Output Monitor while they were the same size before restarting R6.