I use WebClient type to upload *.cab files to my server. On the server side, I registered a HTTP handler for *.cab file with the PUT method as below:
I had this problem but nothing related to WebDAV was the issue. In my case, the client was sending a POST to www.myServer.com/api/chart. This call should be handled by the "ExtensionlessUrlHanlder-Integrated-4.0", however, somehow a local file structure was created in my server directory "...\Server\api\chart\". This meant that the "StaticFile" handler was being called instead. Deleting those local files finally solved the problem.