I didn't saw this in the whatsnew, but it is there:
Edit a part in the assembly environment, than try to open the changed part.
We still get the "there will be things lost" alert, but after a click on the button "OK" (= only button), the part opens anyway.
Just to be sure: what happens? Will there be loss of information somehow?
i justed loaded MP1 and doesn't have te same reaction. Would like to know if it saved your changes