I copied a working config from Windows 7 64bit. Running stunnel 5.50

It looks like your stunnel service was installed with stunnel older than 5.63, which fixed this bug.

Try reinstalling the service with "stunnel Service Uninstall" and then "stunnel Service Install" Start menu shortcuts, or from an elevated Command Prompt with:

"C:\Program Files (x86)\stunnel\bin\stunnel.exe" -uninstall

"C:\Program Files (x86)\stunnel\bin\stunnel.exe" -install