For some time now, I’ve noticed that when I double-click on a time component in a timing (say, hour or minute), it doesn’t always highlight. The entire timing gets highlighted as a row, but the time component does not.
This is not consistent. Sometimes the component does get highlighted, but more often than not it does not. I believe that the failure to highlight occurs most often if I open the Main Window from the menu icon and then immediately try to double-click on a time component.
If, instead, after opening the Main Window, I click out to the Finder or another app and then back to the Main Window, the double-click usually highlights the component.
So it seems as though the time components don’t realise that the window is active and so don’t highlight when clicked.