RMSD Calculation failed

HI,

I am trying to determine the RMSD of an original pose of an ligand (from Crystal Structure) to the poses generated from the same ligand (after docking in CDOCKER)

There is once I could able to do it. (as attached RMSD calculation against the original pose)

However when I repeat the whole step again i cant able to find the RMSD  (as attached RMSD Calculation against the original-failed)

Kindly pls advice on this
Thank you very much

Mai