@apps
Ok sorry - I was finally able to recreate the bug when using pinch-zoom. Took me a while to understand what the conditions needed to be in order for the bug to appear.
If I open an image, and there is still the button that says 'image has loaded, click to view', then there is strange behaviour if I pinch-zoom and then try to scroll.
But, after I press that button to view the fully loaded image, everything works fine, and I can scroll around the image with no issues.