I'm getting double level indicators, like
 Grove of the Ancients
Check all of your quest AddOns, only one should be showing the quest levels. If you have more than one doing so, they will prefix the level and (as you've noted) the next AddOn add it's prefix, as if the quest title includes the already added prefix.
If it's locked, try holding down the Alt button to click those. (It's what I do.)
Thanks Doggabone, that works!
Is there some way to change that behaviour though? I don't really want to have to hold the ALT key just to click the buttons or move the frame ... I notice you said 'If it's locked', but I don't see an option for locking/unlocking the details pane (just one for the tooltip, if it's detached).
If you ALT + Right Click, you should see a short pop-up menu with the Lock option. I don't remember off of the top of my head, but you may need to click near the edge of the frame for the menu.