I also tried using "keyless" for the key, on both score and part - same problem.

Create a new tympani staff first. 

I did that early on, and it didn't work as the glitch happened when copying to the staff, to the external document, anywhere.  Keyless, same keys, key signature there, not there - nothing worked except when I saved a renamed copy of the score, deleting all staves except timpani, exporting to MIDI, importing the MIDI into a new document, and then adding the articulations back in which of course were all gone.  But it had the correct notes at least. 

William the version differences don't matter.

You are trying to copy a timpani part with a certain key sig to a new document with the same key sig and the notes are not the same?  You have checked your transposition on both docs.  Keep in mind that choosing a keyless key signature has no effect on transpositions. There is a big difference between it and Hide Key Signature and Show All Accidentals. That still treats the region as having a key signature.

Yes, keyless simply assigns whatever sharps or flats are entered directly to the notes in the measure without a key signature but does not transpose. I switched to keyless in case there was a transposition being done in error in the new document. But none of the staves have any transposition - they are all either keyless of in the key of C. Also, I tried having them both keyless. I did get the part copied OK by using MIDI. It still won't copy normally but doesn't matter.

Thanks for writing anyway,  Hey!  since you are president of a concert band - here is a Concert March composed in 1976, only played once so far (though maybe will be played elsewhere this year).  Please consider it for your band (Shameless self-promotion I know!)

https://youtu.be/sRb82ZuncxM?si=WiKqw2jTSi-2ZSs4 

Ha-ha - THAT stumped you, didn't it?    

Possibly but since we don't haven't seen the file, I can't rule out a cause. Look most of the time Finale and/or other software programs do exactly what you have told them to do. Not necessarily me but this forum has some of the top Finale experts available. I have no doubt they would have an answer or a why.

I listened to your concert march. Pretty nice a fine job for sure. Kinda Star Warish. Our concert band is a community band made up form musicians form every genre of the community.  From people that just want to play their instruments to professional musicians. I go over every part to make sure our people and concerts are successful. That said I doubt our current timp picker could play the timpani part.

Yes, the timpani part causes some problems!  

Actually that piece has nothing to do with Star Wars - it was composed and performed by the University of Nevada Reno Concert Band in 1976, two years before Stars Wars came out. The only John Williams I'd ever heard was Lost in Space.  The march has more to do with Miklos Rosza, whom I was obsessed with (and still admire greatly).  

Two years ago I had a graduate student from KU that could play it. He has since graduated with his Masters degree and moved away.

The wife happened to walk through the room I was playing it and said, "Another Star War tune?" I replied sorta sounds like Star Wars doesn't it. Being mentioned in the same conversation with John Williams is pretty tall company.

I am guilty of writing stuff my concert band can't play, too, so I can't criticize too much. 

https://www.facebook.com/profile.php?id=100090227538464 

Back to your query if you care to share the file with myself or one of the others let us know. Best to put it in a Drop Box and link us. I am certain one of us will find the cause and answer.

William it looks like you mixed major and minor key sigs. Once that is corrected it copies correctly.

The music is modal in sections, so "major" or "minor" keys don't really matter - it is the exact sharps or flats in the key signature which matter.  Also, if I change from B major to g# minor, and check the box to hold notes to original pitches, chromatically - Finale transposes it!  To different pitches.  This is nonsense.  So there must be some corruption in the file.  On top of that it still does not copy correctly from the timpani into a new default document, which should be copying everything - notes, sharps, flats, key - from the original document, but instead it copies it an TRANSPOSES IT.  That makes no sense.  And it is a transposition that has nothing to do with major or minor keys.  Anyway, thanks for looking at it - I fixed it with manual changes.  

Perhaps I am not totally understanding but as you can see when major and minor are correct in both the new and current doc, Finale copies correctly. This is the way and how it should work.
It’s good you got it the way you need, though.