Open a fresh server.
Create a VI Pro.
With the Group option open, create Group 1 at the bottom of the Mixer channel.
Copy the channel set.
Create a new instance.
Paste the channel set.
Go to the Group slot of the pasted channel and set the Group to None.
Here, it faithfully crashes the program. (I have sent the log and the file, though I subsequently see that even a fresh instance causes this behavior -- the file is irrelevant.)
Moral: be cautious when pasting a channel set assigned to a group to a new instance where there is no group.
