Problem with NVENC export in 16x9 and iPhone

I use the Adobe Cloud sync to move video files from Windows to my iPhone. It usually works alright, but since the introduction of the NVenc hardware acceleration feature I haven't been able to download videos in UHD 16x9 to my iPhone. Videos in 1x1 are fine. Google Chrome on the iPhone won't display them either, if I link the files. Having tried well over twenty files I came to the conclusion that it must be something with the NVenc files and I have found that, yes... it is!

I exported two identical files in UHD 16x9, one with the old software method, one with hardware acceleration, both uploaded fine but only the software encoded video downloaded to my iPhone.