Actual notes are changed if transposition properties are changed with Concert Pitch off

Steps:
1- Create new score for Bb Trumpet in C major (actual key). Initial key signature for the generated score (for this transposing instrument) is D major (2 sharps).
2- Insert four 1/4 notes in the first measure: D E F(by default it is inserted as F#) G.
3- WITHOUT entering in Concert Pitch mode, right-click on an empty measure and choose "Staff Properties...".
4- Set "Play transposition" to "0 - Perfect Unison" ( + octave 0) and click OK.
Results: the written notes remain the same even if the transposing properties have changed; the actual notes ("Concert Pitch" on) have changed and thus during playback the notes sound a tone higher than before.

If the same steps are performed with "Concert Pitch" in "on" mode, the transposition behaves as expected, i.e. actual notes remains the same (with right playback) and written notes for the transposing instrument ("Concert Pitch" off) change accordingly to the new transposing properties.

Notes: this problem also applies if "Change Instrument" to a different transposing instrument is chosen.
Keep in mind also issue (possibly solved?) #6281: Instrument change undo, transposes twice (I noticed this behavior while trying to reproduce the issue with the most recent Nightly).

Nightly Build rev. 0e89256, Windows 8.

Marked as critical because notes are automatically changed to the wrong actual pitch, even if a work-around does exist (= transpose the staff).