Checking in the file without saving it in SolidWorks first does not save the changes. You must save first.
Another thing you must remember is that the ability to see the latest version of the file is dependent on the permissions that the user or group has. For example the group that the user belongs to might only be able to see the latest version of the file when it was in the Released State. So if they cannot see a file that is in Work In Progress, they will not be able to see that version at all.
I've had situations where EPDM does not force the next user to see the latest version. Even when there is clearly a newer version available. Generally a simple "get latest" is all it took to resolve the issue, but occasionally you'd have to wait a few minutes for the new version to show up.
I noticed it more at a client that had replicated servers that were several hundred miles apart, the replication happens at regular intervals but not instantly.
As far as a forced save before check-in I really don't know.