fcpx frame errors keeps stopping my export

To delete preferences, hold down command and option while starting FCP X and click Delete Preferences.

The application will start in a default state, and open an "Untitled" library. Reopen the library you were working on, set the preferences the way you like them, and try again.

Usually the recommendation is to turn off “background render” in Preferences->Playback (*)

and export without rendering first.

(*) by deleting preferences this option is turned on, so you may want to turn it off again.

The clips may be fine for playback but not fir encoding. Please give the complete specs of the media from MediaInfo or Invisor. Are you using any third party plugins? Are you doing anything aside from cutting the video?

Does the problem only occur in one specific project?

I can think of two possible causes: either some bad media, or a subtle corruption in the project.

One thing to try is: select All in the project; Copy; make a new project with the desired frame size and frame rate; Paste.

If there was some subtle corruption in the project, usually the new one works well.

To look for possible bad media, you can try the divide and conquer method: set an out point near the middle, export just one half; does that work? and so on.

if the problem persists, Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

Delete All render files. Delete FCP preferences.

Any changes?

what you mean by cutting the video ? Editing. Or are you doing effects, transformations, keying, coloring, all the things you can do in software?

MediaInfo and Invisor are in the App Store.

Right click on one of the files and select open with MediaInfo. Post what's in text view, the third button at the top.