iMovie Clips Stutter, Drop Frames in Timeline

iMovie has suffered from this issue for upwards of 5 years, and it is infuriating.

When I put footage in the "My Media" section of my project and watch it, it runs smoothly in its perfect 60fps. However, when a clip is moved to the timeline of my project, it stutters and drops frames in areas. It doesn't happen to every clip, and it doesn't even happen to every part of a clip; it happens to random sections of all the footage I put in the timeline with no rhyme or reason. Audio playback is unaffected. The stuttering shows up a project once it's exported too, so it isn't purely a visual issue.

Let me be clear - this is not a question of the app lagging as a whole. All my inputs are buttery smooth, and the editing process is unaffected. It is only the frame rate of utterly random parts of my footage in the timeline.

This is not a hardware issue. It is a simple 1080p 60fps timeline with no transitions whatsoever. My hardware (M2) is not the issue, and is capable of crunching far more demanding tasks than this. I've edited in Premiere Pro and Final Cut in 4k without issue. My SSD is nowhere near full.

My footage should 100% be compatible with iMovie (1080p 60fps MP4, H.264 codec). It's not a question of the project frame rate differing from my footage frame rate; all clips in the project are from the same source (the project should set itself to the frame rate of the first clip in the timeline, I'm told), and some patches of the footage run at 60fps in the timeline anyway, so it's not an all-encompassing compatibility or playback issue. The files are not corrupted in any way.

This issue has persisted across years, across multiple projects over the course of those years, across different Apple devices with various different performance capabilities, and numerous different versions of the app and MacOS. It persists upon hardware and software restarts. I've had friends and family experience this issue, and I've gone through old Community Posts on this site from six years ago discussing the same topic.

There have been no fixes provided in all these years.