Can you confirm how the iPhone videos are getting to CC please? Like, as a USB connection to your desktop, or through the iPhone Lightroom app or another way? And which iPhone version are you using? On which operating system version?
...sorry, for some reason I didn't get an email notification on this. The pix are getting to Lightroom CC via import from the Lightroom CC desktop app. I have an iPhone 10, the latest iOS release. On my Mac, I have the High Sierra OS.