Hi there and welcome
this is usually caused by a faulty clip in the film so you need to find which one it is.
The easiest way is to do the following
opened the problem project and hit select all and copied all the clips.Then go back and start a new project. Paste your clips. (you will only have your video clips and not any audio.)At this point just start from one end or the other and delete one clip at a time and try to export.You should keep getting the error until suddenly it works.At that point you know the clip you just deleted was the problem clip.Go back to you original project, find the problem clip, remove it and replace it with the original
Then try to import
Let me know the results please