Photos app color shifting in real time?

I’ve just exported a video I worked on in Davinci Resolve to post on Instagram but in my photos app there’s a weird color shifting happening in real time. As I swipe to or open the video, the color goes from how it should look to a slightly more washed out version. It’s a split second sudden change. I’ve turned off display full HDR is my settings, and this isn’t even an iPhone video. It’s a fully graded and exported Rec 709 file. I managed to screen shot quickly enough to catch the shift here. More saturated is how it should look, but it immediately washes out and plays with that look. Has anybody experienced this and found a fix?