Thanks for all of your patience. This issue has been reported to the Presonus development team. Basically, the crash only occurs if you are copying voice 4 of the bass clef of a grand staff into another bass clef of a grand staff. To avoid this, you will want to use voice 1 and voice 2 in the treble clef as well as voice 1 and voice 2 in the bass clef. If you need to correct a score, just use the "Select Special" and "Paste Special" options to paste your notation into the desired voices of a new grand staff. You can then just copy/paste the treble clef into your new grand staff and delete the problematic one. "Select Special" and "Paste Special" are both found from the right-click menu, when you right-click on some highlighted notation.