If you just found out that OBS has failed to document the memory limitations of its 'Image Slide Show' source... And that the randomization method used isn't a shuffle of a list, but a random individual selection... And that the randomization seeding method used heavily favors certain positions in the list of images... And that someone fixed the issue in early 2021, handed the solution to the team with a bow on it, but they still never implemented it...
Yeah.
...Then this is the fix for you! Simplest possible solution, right here. An html file that runs some javascript to make the slideshow happen, and a LUA interface to let you change configurations, and refresh your image list, on the fly, inside OBS.
Takes a bit of work setting up (pay attention to the instructions! and don't unzip this into your OBS folder under \Program Files\ on Windows or the UAC is going to give you issues with administrator priveleges) but it's the simplest, minimally invasive solution imaginable. And I thank the dev for it!