"Play with right hand" in Master palette
MS 126.96.36.1991...; Windows 10
This one will be hard to explain because the behavior is not consistent and may be difficult to reproduce, but I've seen it multiple times.
When I open and use the Master palette for the first time in a session (I say this because once I get it to work right it keeps doing so in that session) and I select Symbols, Keyboard techniques (with the default Bravura font) and click the Play with right hand bracket (or the Play with right hand (end) bracket) onto a selected note in the score (and optionally close the Master palette) the brackets are dropped almost onto the selected note, so I want to change their X offset slightly. So I click on a bracket to select it. It is indeed selected and editable in the Inspector, but it does not turn blue; that visual indication is lacking. When I change the X offset, a "copy" of the bracket is moved, and is blue, but the original bracket remains black and in place. Yet they are really the same bracket. Try deleting them and see what happens; you can delete the blue one but not the black one until you have deleted the blue one. Then the black one becomes properly editable.
I tried it with the Play with left hand brackets and this did not happen, but it may have been influenced by what I had already done with the Play with right hand brackets. So I cannot say without further testing whether the same issue occurs with them.
It might be that the Master palette is dropping a double instance of the bracket into the score. What I have observed would be consistent with that, but I've not taken the necessary steps to prove it.