Depends on the source media. Do you have valid TC and unique file names on all clips? The easiest free solution might be to wash it through Resolve. Or maybe use Automatic Duck (FxFactory), but that probably means FCPX to AE to Premiere to AAF.
Or, just export a flattened timeline with some handles. Of course, then you lose your links to the source media, but it still might be the best solution if the others don't work.