t sounds like you have a touch event propagation issue. stopPropagation() and preventDefault() are used to prevent the event from propagating to parent elements, but in your case, the event is still propagating to the parent div. Here are a few suggestions to try:
Use the touch-action CSS property to control the touch behavior of your child div. For example, you could set touch-action: pan-y on the child div to only allow vertical scrolling within that element. This should prevent the touch events from propagating to the parent div.
You can add an event listener to your child div that captures the touch events and prevents them from bubbling up to the parent div. For example: