My iphone 15 pro at 4k24fps video stutters

I too have the same problem. It’s not related to iCloud as the other commenter mentioned. It is a genuine file issue. Did you find a fix?

I which device are you playing back the video?

Probably you have enabled iCloud Photos and have a poor internet connection.

It would appear that it is the speed of the cable that I used to connect an external fast SSD. When I replaced the cable with a faster one, the problem was no longer evident.