Microsoft tells us " Buy our Microsoft Miracast Adapter ".
That is their idea of a solution --- sell more merchandise.
My SPI sends the start screen to my Sony UHD tv in Mirror mode and then the screen goes black.
The tv and the SPI both recognize each other and the tv is sitting there in mirror mode apparently waiting for a signal which was, apparently, cut off by the Surface Pro because they don't want us to just be able to mirror to our tv's without BUYING their adapter.
It is obvious the SPI is fully capable of mirroring to the tv without an adapter or the start screen would never appear on the tv at all.
I doubt Sony has the tv programmed to cut off the signal because that would cost them sales if word got out that they were stopping miracasting. There is no upside for Sony to do that.
But there IS an upside for Microsoft to stop / change the signal coming from the SP --- they sell more adapters because it won't work unless you get their adapter which fixes the signal so the Sony can see it again.