I just want to sort my images in the gallery into the file name order yet there doesn't seem to be an option to do this?

Why does it change Every! Single! Time!

Actually nothing changed. It's the same as always actually:

• Options > Gallery > Sort gallery by: Global order for albums and subalbums
• Options -> Image > Sort images by: Global order for images
• Each album page has a options for the sort order of its subalbums and images.