Repeatable FCP 11 bug - Missing or offline titles, effects, generators, or media

Upon attempting to export a single project with a single 12sec clip I can get this warning using no third party adjustments, effect or generators. Disabling simple Sharpen and color adjustments makes no difference. If I snapshot the project it will export with no problem. On another 3min project also with no 3rd party plugins or effects etc I get the warning and ignore it an export and the result is just fine. Many of my project give this warning but not all. In one case I removed an adjustment layer and that "cured" it but in many cases there are no effects or generators involved at all. In all cases creating a Snapshot of the project allows it to be exported without the warning but thus far ignoring the warning also is just fine.