Random Frames after Sharing

Hi

I am a newbie on using the FCP, tried to make a video however I keep getting a random frames (which happen randomly for less than 1 second) after I shared the video.
I got the video from my iPhone (1080p 60fps) then imported to FCP media.

My project settings are:
1080p, 60fps
Shared as master file 1080p (tried youtube as well however there are still random frames)

I have cleared my render files (from project and library) as well as turning off the background render, however the issue still persist.

Thanks for the help!

Try optimizing your media.

I edit iPhone footage daily, and I don't have these problems with my exports. Can you give us specifics? What are your iPhone video settings? Mac model and specs? macOS and FCPX versions?

There have been quite a few reports like this on Apple Support Communities.

I have seen this in one other person's FCP exports. What I think it is is that there are video tracks on top of the video that's on the primary timeline. Some of these clips on top are not butted together properly so the video underneath shows through for one frame. Can you check that?