FCPX Stabilization issue with videos shot in portrait mode

I have Sony FX30. When a video is shot in portrait mode and stabilisation is applied in FCPX it make the video even more shaky. I have spent a lot of time figuring out the cause and finding a workaround.

It gets fixed when the video is transcoded (optimised). After this procedure stabilisations works fine. I guess it is a codec compatibility issue. I would appreciate if developers fix it in future updates.