i was facing issue for my project preview already because of lots of animations so I swapped out all my animation for lower frame rate versions and lower quality images also.
I can load preview for each page individually, but the software keeps hanging as I try exporting the entire book or when I try seeing preview for the complete project.
It keeps getting stuck at "building cover page" ( for exporting with or without cover page )
I saw same error being posted by other users also on pub coder forum but no one has replied with a solution.
I don't know if it's a software issue or my laptop because my laptop also blue screened multiple times when trying to export the project.