Hidden Horizontal Overflow
In some cases, there might be an element that is literally wider than the document is, which might cause horizontal overflow scrolling. You could use a little JavaScript to help you find the culprit.
const documentWidth = document.documentElement.offsetWidth;
document.querySelectorAll('*').forEach((node) => {
if (node.offsetWidth > documentWidth) {
console.log(node);
}
});