iPhone 11 Pro and One R - Stutter playback on iOS app

Hi - just getting started for the first time with my One R (my first time using Insta360 products too. When I try to edit small or large videos on my iPhone 11pro the playback of the video is intermittently stuttering, making the edit process clunky and not a great experience.

Any ideas?

Iphone 11 pro, latest iOS, latest app version and latest one r firmware

SanDisk Extreme 128 GB microSDXC Memory Card