Create new part: partname is ignored and gets default name "Part"

System: OS X Yosemite 10.10.5
Version: MuseScoreNightly-2016-11-03-1931-master-221f20b.dmg

If i create a new part via the "Parts..." Dialog and enter a custom name "2nd Cl" for it, after hitting OK the entered name is ignored and the new part is just called "Part".
Create Dialog:

If I go back to the Parts... Dialog and click on the newly created part, there are no instruments in the instruments in part list.
If i change the name again and hit OK the name changes correctly.
After saving and opening the file, the missing instruments of the part appear correctly.

Create Dialog (after OK):