FCP 5 Funkiness - Bug?

Has anyone encountered this - easy fix..but annoying in FCP 5
(this is under System 10.4.2 and Quicktime 7.0.1)

Render a nested sequence..

Then go and try to change something inside that nest.....requiring a re-render

Go back to main timeline where the nest appears - The main timeline still thinks everything's hunky dory....nothing's changed.

The only way to get the nest to reflect the new "internal nest" change - is to apply something - anything to that nest as a whole (blur the nest) Then the old render goes away and you get what you changed inside the nest)

It's a simple matter to just remove whatever filter you've added to the nest....and then re-render.

Any idea why this is...bug? Undocumented "feature?" Inquiring editors want to know.

Thanks Andy