Why is a conditional formatting range mis-applying some cells?

I have a google sheet with one conditional formatting rule defined:

This is the only formatting rule in the sheet:

As you can see, Q3 is not obeying the rule. And when I test, neither is Q2. At some point I've inserted new rows at the top, but then I would expect my conditional formatting to show it is missing those cells and it's not.

What is wrong and how do I fix it? If it's not clear, the point is a whole row should be green if the Q cell is empty.