Hi Rob, I have had the identical problem since late 2018, which seemed to coincide with W10 1802 and now 1809 update. Igor was very helpful in trying to sort it, pending PTE10 release, but the problem has remained with my latest published project . Like you I use converted video clips and I also show single images, moved on by mouse click, which I describe to the audience (often photographic societies) during my presentation, so I need the flexibility of the exe format so I can not publish it as MP4.
Igor said it was an issue with NVIDIA graphics card and W10 updates, so like you I am rather stuck pending PTE10, as I use PTE frequently for lectures - unless any new suggestions are made
John