Insufficient Space when exporting large iMovie projects

Hi,

I'm trying to clean up an iPad with a large number of iMovie projects - I want to keep the projects, so my process has been to export the iMovie projects as bundle files and then move them off the iPad into iCloud. This process works, except for when dealing with larger projects - I keep getting the warning "Insufficient Space - there's not enough space to share your project." This doesn't make sense, as there is plenty of space still on the iPad to work with (as the attached images show). Anyone have any ideas on what I can do? The "available" space tends to fluctuate, so I have no idea if it's referring to RAM or some other temp space - quitting iMovie and rebooting the device don't seem to help.