1) On the cell rename the file ../pw/server/etc/<CELLNAME>/kb/classes/mc_sm_object.baroc to mc_sm_object.baroc.old
2) create a new copy of mc_sm_object.baroc by running the command
pclassinfo -q -x -o mc_sm_object.baroc
and place it in ../pw/server/etc/<CELLNAME>/kb/classes directory
3) Recompile the cell kb :
cd $MCELL_HOME/etc/<CELLNAME>/kb
mccomp -v manifest.kb
4) restart the cell
5) Promote/Publish again