Strange. Can you try it from 32-bit commandline?
C:\Windows\SysWOW64\cmd.exe
Before posting, please read how to report bug or request support effectively.
Bug reports without an attached log file are usually useless.
C:\Windows\SysWOW64\cmd.exe
Shift
and Ctrl
keys. Instead of executing the extension command, WinSCP will copy it to the clipboard. Then paste the command to Windows command-line and see (and post here) what it outputs.