I need to sync existing work items, however the sync fails because some of the newly added (not very new though haven’t synced for couple of months) fields are mandatory.   

When I try to update their values (one column at a time) it fails again because the other required values are not set, obviously!   
 
Any suggestion on how to handle this issue is much appreciated.   
 
Something that came to my mind is removing the mandatory fields from operation behaviour, make the changes and when done set the mandatory fields back. Might not be very practical.   
  

Thanks   
 Nag