Just to clarify, the steps that you are following are:
- unlink dev database from repository
- restore prod database backup
- relink new dev database to repository
- change sproc and attempt to commit change
Before you make any changes are you checking whether you are on the head revision using 'Get Latest'? Is the tool picking up the revision number allowing 'Get Latest' to work? When you complete the change is the little blue blob appearing in SSMS before you go to 'Commit'?
Technical Support Engineer