Interpreting between the Center of Mass and Center of Rigidity.
Check if superimposed dead loads (SIDL) are applied correctly. etabs mass summary by story better
Check if you applied property modifiers (like 0.0 weight) to certain elements. Interpreting between the Center of Mass and Center
If you'd like to dive deeper into the technical side, I can help you with: The for mass source. How to export this data to Excel for faster reporting. etabs mass summary by story better