If you don't want players to be able to change their CSR/Average/Ranking on the scoresheet, we have an option to make the average box a "read only" for the players.
Go to Menu > Manage > Round-Robin/Bracket > Round-Robin.
Select the round-robin.
Click on the Pencil to edit.
Go to Advanced section.
Check the box to make the average box a Read only.
Player handicap on scoresheet is read only