This was a limitation due to case locking and is addressed in 7.3 release. Please find below the snippet from the release notes.
Cases no longer locked when followed
Work party properties of the type follower are no longer associated with the cases that you follow. Cases are no longer locked when you follow them, so now all users can follow a case. If you upgrade to Pega 7.3, you can run a utility to upgrade the cases that you are following so that they are no longer locked when they are followed.