Hi Alex, I’ve just tried it without the PnP code and the default value set in the list appears to update the item. I then dropped the code back in and although my ‘new’ number shows up in the title field as it is saving, it then reverts to the default value in the parent list control. I thought maybe it was a timing issue but refreshing the control kept the same default value.
I’ve added other updates to field values in the (child) form in the fd.spBeforeSave handler, they seem to work,only the Title field does not update for some reason.