Lumia 950XL + Latest Official Win 10 ... cannot record video to SDcard

[Sunstorming]

Anyone know why on my Lumia 950XL I cannot record 4K video to my UHS-II / U3 rated 60MB/sec write tested and verified SDCard? Whenever I try this, it seems to work. However when I go to watch the video, it's 6 hours long (even if it was actually a 1 minute recording) and plays a few seconds of a song in my Music folder?

If I record to the internal memory, it works flawlessly. And before you ask, I have tried TWO different, verified working SDcards with the same results.

What gives?

 

[daimv]

Is it just with 4K video? i.e. if you record video with any other resolution/framerate does it work fine?
Also have you tried using other video recording apps? Like Proshot, for example.