EHttpApiException -unknown-

I don't know, where I have to search.
I have a XData Server (console prog) and use Aurelius with MS SQL.
My client first sends a "GET" to get the person data.
Then I change one field (only text) und call "PUT".
The changes are stored, but I get an error in my log. See picture.

I don't know, where I can locate the error.
The response is 200

That's a normal error that happens when the client is gone and the server tries to respond to it. You can ignore such error.

Ok, I do it. Thank you, Wagner.
But, if it's normal, why comes the error?
Can I do something to suppress/prevent the error?

Well, it's an exception raised by the HTTP Api, so we didn't mask it. You can simply check for it using a try..except and ignore, if you wish. We are considering adding a property in future to ignore that specific exception.