The minor ninth is considered the “last dissonant interval”, even more than a minor second. Therefore it should be handled with care in any chord voicing (including minor ninths + octave(s)).
The inherent dissonance in this interval will often dominate the rest of the chord structure and weaken its transparency. Especially on sustained chords in the orchestra, this harsh dissonance can create quite a bit of destructive force in otherwise maticulously crafted orchestrations.
Highest risks for involuntary minor ninths are unfortunate voicings of the following chord types: Maj7, minor9th, #11 chords (click on the chords for “unfortunate” voicings containing a minor ninth).
However, due to the fact that dominant chords are supposed to create a lot of tension to create a fullfilling resolution to a tonic an inherent minor ninth can sound lovely in such a dominant situation.