Other users can edit/save checked out file

Hi!

I am using RCS v5.7 on a Windows based system.  The files are stored on a
network drive.

I have checked out a file (w/ a lock) - this completes successfully - I get
a message saying the file is locked.

Now, another user is still able to open the file, make changes, and then
save the file.

What are we doing wrong?

Thanks!