I have seen this several times on 5.13. To repeat:
1. In WinSCP, display a directory with files on the server. Pick a file(s) and copy to your PC.
2. External to WinSCP, change (edit) the file(s), like through a putty session or something.
3. Back to WinSCP, copy the file(s) locally to your PC.
4. The file(s) copied are the old versions before the changes. Granted, the time stamp in the WinSCP commander window still shows the old time stamp for the remote file. But in previous versions of winSCP the updated file(s) were still copied. That does not appear to be the case, as if WinSCP has cached the file(s) or something.
5. Now, if you do a 'refresh' on the files in the WinSCP remote Commander so their time stamps update, THEN copy the files as in step 3, the correct update file is copied.