i had similar issue with recent putty versions ( around v0.66 ) that was fixed by changing the Remote Character Set for site under
Window -> Translation
in the putty config from UTF-8 to ISO-8859-1
i can't find anyway of doing that with WinSCP 5.9.x so it's impossible to login to affected servers using 5.9.1
5.7.x versions don't suffer from this issue - presumably based on older version of putty which also didn't show the problem
any chance we can get the option change Remote Character Set for sites in WinSCP as per putty config ?