Scroll bar in photo library

Having 30,000 photos in the library I’ve noticed a problem. The scroll bar to the right of the screen is extremely thin. When trying multiple times to touch, hold, and scroll, if you don’t get it right, photos become selected with the blue circle check box. This causes the user to have to stop, uncheck the multiple photos, and try to scroll again. Why has it been designed this way? Sometimes it takes 7-8-10 tries to get the finger positioned just right on that thin scroll bar. (Update) This is specifically in iMessage when trying to select a photo to send. The library scroll bar starts at the top and scrolls down.