Exception in Session.SynchronizeDirectories

Dear WinSCP Support,

We encounter a problem by using Session.SynchronizeDirectories used in a PS script.
See script in attachment as private file.
-> WinSCP Version 5.19.1 (Build 11552) (OS 10.0.19042 - Windows 10 Enterprise)

An exception is thrown.
The WinSCP log file reports following error:

451 Internal error.

See attached log file.

Thanks.

The error comes from the FTP server. Please contact your server support.