Photos Slideshow Text Unstable

I store my photos in iCloud and have a fairly large library (about 10,000 photos). My wife is building a slideshow of our recent trip to the BVI and has selected about 390 photos to include in the slideshow. She first added all of the desired photos and started a project. Once in Project, she has been adding text to many of the photos. After adding text to nearly 250 of the photos, all of the text on all photos disappeared. It appears that there is no way to retrieve the text lost on those photos. After scraping my wife off the ceiling, I had her start over. This time when she was on about the 50th photo, all text previously added again disappeared. She has spent many, many hours to this point and it seems that Photos for Mac or the slideshow capability within Photos has a problem. My questions are:

1. Are we doing something wrong

2. Have we exceeded the capacity of photos or slideshow slides

3. Should we be using some other program to build a slide show and if so what program.

4. Our intent was to build the slideshow with text captions then save in iTunes and then transfer the slideshow to DVD's to share with others that enjoyed our vacation with us.