HELP please: Extracting individual parts on multi-voice staves causes unexpected result. Missing/Deleted last measure.

Hello, I'm hoping someone might be able to offer solution. I am a new user of MuseScore, coming from Encore. I have attached a Score that was imported into MuseScore as a MusicXML file. The Score itself imported just fine. My problem is in extracting individual parts.

In the attached Score there are a mix of single voice parts along with several multi-voice parts, I am looking to save the individual parts as a PDF for each musician.

When I use the "Export" feature via [File/Export pdf/Each part to a separate file] everything works as expected. I have done this with all of the single voice parts without issue.

My problem occurs when I have a multi-voice part and I use the "Parts" feature via [File/Parts/Open Selected]. When I do this, things start out correctly, but when an individual voice is selected in the Instruments pane in order to create a pdf document for each voice individually, the last measure of that voice's part is replaced with a measure with no notes, but just a whole rest. After this you cannot go back to a corrected state until you exit without saving and reopen the file.

I have looked through both the documentation and the forums to no avail and am hoping I am missing something obvious.

As a specific example, the first multi-voice part in the Score is "1a e 2a Tromba" (this is an Italian piece). When you extract that part with both voices the last measure is shown correctly. However, when you then select only one voice through the Instruments pane, the last measure is deleted and replaced with a measure that contains only a whole rest.

Not sure if there could be something in the original XML file with respect to the voices that is creating this glitch?

Thank you in advance for any insight into this issue.