Changing a Voice Instrument

No matter what I try, I cannot seem to change the “train whistle” upstem triads at the end of this sample from Piano sound to Flute either in NP or HALion. In Play mode the notes seem to appear as slot 3, downstem voice 2. I wonder whether there was some hidden MIDI setting in the XML import form Finale that is blocking this, but I do not have the tools to examine this. It’s a relatively old file that I am trying to bring forward into Dorico just in case somewhere down the road I no longer can open it in Finale.

Any thoughts? (932 KB)

Assuming you’re talking about the Bsus4, it’s showing up here as Up-stem Voice 1, and HALion has it on channel 4. I don’t seem to have a problem changing that to whatever I like.
I’ve attached my edited version.
pollersExpressDorico201017 (999 KB)

Right you are. I was apparently not looking at the proper register of the piano-roll in Play.

Many thanks!