I have a 6 minute timeline with a number of liquid morph effects. One of them refuses to render. It's just a few seconds down the timeline from several other identical effects that render fine. This is not even nested. It's just a 10 frame morph. I have tried deleting the effect and re doing it and have tried every way I know of to render - render in/out, expert render, prepare for digital cut, render with the render button, render in the effect editor. I went into media tool and deleted the last 8 or so media files from my attempts to render, but I probably left a few older ones in there because I couldn't identify them and didn't want to destroy other effects unwittingly.
Out of some 145 effects in my timeline, this is the only one with a problem. I tried moving the edit point 30 frames forward but it still won't render.
The source files are Avid DNxHD145 media files that have been transcoded from h264 Canon 5D original files.
Suggestions? What could be causing this?