Ah, sorry I guess I wasn't clear. all images on single subfolder - up to win 8.1 there was no issue regarding slideshow from subfolder, once into win 10, doesn't work and I see no setting methods...

Yes they are all .jpg files - they are in subfolders, not directly off "pictures" folder

windows explorer image folder files do not cycle through all the images in file on slideshow (just cycle though 30-40 images and repeats)
How to change setting to cycle through all images in a file...