What you can try to do is create small sections for this slideshow, so instead of loading all the images at the same time, try to do a small batch of files, export them, and repeat the process. At the end you should have some videos with your slideshows, so you can just load the videos and export them as a final project.
There a many more steps, but this could help you to avoid the program crash and that you can apply the transitions without a problem. If you still need more help try to contact the technical support team, they can also assist you, and you can contact them here:
https://www.nch.com.au/support/supportcontact.html?software=PhotoStage&support