Lightroom 5.7 dropping last added photos and text in Book file

Hi,

I'm using Lightroom 5.7 on the Mac to create a photo book in the Book module. Recently, it's started to drop the last photo I added or moved or some text I added from the book file after I quit LR. Anything I do before I quit, LR, such as export a pdf, will be fine.

I don't think it's possible to Save the book file before quitting LR.

Any suggestions?

Thanks.

Ellen