Abstraction stacks hiding complexity all the way down. Maybe the kernel touch driver sometimes reports duplicate events due to a race condition, so the user mode library drops events it thinks are duplicates... Maybe the application changes some shadow DOM state when you touch and the framework ignores events while the real DOM is out of sync and thinks it's also being clever by deferring the DOM sync... Maybe it's just polling every 200ms for a current touch.

Once I tried writing an app in early windows style: inside the mouse down handler redraw the button as pressed, etc. Not setting the button state to pressed and triggering a redraw, but actually changing the pixels inside the handler. It's a huge layering violation but it's actually refreshing to cut through all the BS and make the computer just do the right thing, and it actually worked better most of the time than a modern framework app.