I created a project, did all my cutting then within the project, selected all the project contents to create a compound clip so that I can place some mastering effects on all the video (broadcast safe) and all the audio (levels / limiting etc) (if only there was a mixer!). Checked the compound clip, all good. Checked a few seconds of the Project (with the compound clip in) all good, so then share->master file (output is prores).
On test review of the master file, just before the end there is a flash frame from the very beginning. Not sure why because it's not in the compound clip (the original edited timeline).
I then review the project (with the single compound clip inside), and there it is, the flash frame, even though it doesn't appear in the actual compound clip itself.
Naturally (well it is for me!), I selected the event and deleted all generated render files assuming this was just a render cache problem.
Re-Shared, and tested again only to find the problem is still there.
So it's not in the compound clip, just the project. Very odd. Process I followed was, create new project, copy contents of compound clip to new project, delete the compound clip and the original project, renamed the new project, then select the contents and created a new compound clip, and re-applied the two master effects. Send off to render, tested the output, all is good. In other words, recreated the compound clip and the parent project.
It appears there are many little gremlins in FCPX unless I am either doing something fundamentally wrong or my expectation that it should be consistent and reliable needs re-adjusting.
Is there a simpler, more reliable way to avoid and fix render issues like the one I describe here?