Are you sure it really did transfer?
This can happen when the storage on the server isn't correct.
It can also happen when the server half of the transfer has a problem, and doesn't actually save the file to storage, and doesn't correct the client (false success).
I assume you're using GUI due to use of the word "settings" so it won't likely be from a bad user made script in this case.
You might want to provide a WinSCP log. But, that log won't show server side problems that return false success. If there's something else, the WinSCP log may show it.
This problem occurred for the first time today. I looked in the settings but couldn’t find a function to restore it to its original state.
My problem: After copying a file to the local server, the file is automatically deleted from the server. This, of course, should not happen.
Thanks for the help and greetings from Germany.