changing assignments

Hi team

I have picked an HSQC and used Set up NMR residues to give them numbers and assignments to my chain. I then used Pick and Assign on 3D 15N NOESY and TOCSY. Now I am assigning these to real atoms using Peak Assigner. I click edit and change the residue number/name etc to the correct one. I merge the NmrAtoms when it asks. It assigns and propagates to the 3Ds but now the shift is always set to None. I can fix it by double clicking on one of the assignments to remove it, selecting New and doing it all again, but it’s a bit tedious having to assign everything twice. Any idea what I might be doing wrong?

Thanks
Helen