Chord playback and duration

Hi,

When I enter a chord symbol with the slashe notation, the option "until the end of attached duration" doesn't play for the duration of the slashes.

Here how I do this: I put a whole note, then I select the measure and toggle to slash notation. Then I click on the slashe and hit ctrl-K. Then I enter the chord symbol. I do this for the following measure. I then click on the chord symbol and make sure the "until the end of attached duration" it selected. Is this the proper way to do it ? Because then when I start the playback, the first chord plays but never stops. When the second chords starts to play I can still hear the first one... they overlap. What is happening ?

Thank you.