Takes Forever To Open Files (OS X El Capitan)

With the recent El Capitan update, .iba files take forever to load. I get the spinning beachball for 15 - 20 minutes until I am finally able to use the file. Before the El Capitan update, files would load within seconds. I have this problem on a MacBook Pro and iMac running the latest El Capitan and iBook updates. It is ridiculous to wait so long for a file less than 1GB to open. Please fix this issue!

miggiegg about iBooks Author