There is a known issue in Finale with Smart Shape slurs that are positioned across staves that occurs specifically on Windows operating systems. In order to workaround this issue please follow the steps below...
To create a slur that crosses staves-
- Open the document.
- Select the Smart Shape tool.
- Select the slur from the Smart Shape palette.
- Choose (from the program toolbar) Smart Shape > Attach to Beats.
- Double-click and drag to create the cross-staff slur(s).
- You can change back to Attach to Notes (Smart Shape > Attach to Notes) when not creating slurs that cross staves.
If you have slurs that are cross-staff slurs and were created with the Attach to Notes setting, these slurs will have to be deleted and recreated using the steps above.