Sorry you are having this problem. We have been chasing this down but have not been able to get a project that routinely displays it. We do know that if the timeline isn't building correctly, pressing Undo to unbuild the last actions will get you back to before the problem started. Also trimming clips around the last things you did will often fix the problem - but it sounds like you are beyond that point.
Does the export button work? Is there any way you can upload a Project Archive to us. If you are on the iPhone you should make sure that you connect to wi-fi somewhere to do it.
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