I need to reduce the opacity of a piece of video and overlay some pics and a quote. normaly I just split the track and lower opaciaty, then overlap so its a clean disolve. problem is the piece of video has a track motion effect going on at the same time, so overlaying the video doesnt work, there is a stutter when it disolves.

what else can I do?

How about a composite envelope?

not sure I've understood entirely, but could you not just render out the piece with track motion, bring it back in then adjust it's opacity?

When we have too much going on that all conflicts with other things that we need to do we normally render it out to uncompressed and bring it back in so we can start again with other tricks on it that don't have any impact.