you may have to delete the fragment (both pex/psc) in your scritps folder after you detatch the fragment from your object (erase everything in fragment window compile and hit ok to close out, then reopen and detach)
for future refernce, do not ever delete properties that are filled. instead follow these steps to get it working again without the usual papyrus errors:
go to properties, hit clear value
press ok to close the property window, press ok to close the edit window (basically hit ok to close all the windows)
then re-open your edit window and go back to your fragment, edit source and delete the property.
hit ok to close out all windows.
this will delete the property without leaving any residue in the VMAD record