Final Cut Pro Share Operation Failed

Long video, about 90 minutes with two timelines from two cameras. The top timeline is broken into lots of little clips, the bottom timeline is the base view from the main camera. I've done several long videos like this without a problem but now I keep getting the message that the operation has failed (see image). I've tried removing the transitions on each of the smaller clips and removed the effects presets. I've also reset the preferences and removed render files. This latest version, at 1080p took at least an hour, but at least it finished. I'd really like to restore those transitions and try again. First I thought I'd ask if there's a quick cure. I'm using a trial version of FC Pro.