A - Checkerboard Image At Export?
Using a plugin and finding that the media is being lost after exporting?
This will occur when the plugins that are being used are not stored on the same hard drive as the project they are being used in.
When exporting a project that is stored on an external drive, Final Cut will remove all media files that are not stored on the same drive as the project.
You can create an alias folder of your Movies folder by right clicking on it and selecting "Make Alias". Once you have made the alias folder, place it on your External drive with your project.