Scroll bug

My website isn’t live yet so no link.

This is a little hard to explain.
When I scroll down any of the pages, the page scrolls smoothly at first but then it jumps down a little to where the “go top” button is visible. Then it scrolls smoothly again. I scroll back up and once I near the top of the page, it jumps again and the “go top” button disappears. I wish I had a better way of explaining this. It’s not as noticeable when I scroll up and down quickly but if I scroll slowly, it can be really annoying. Has this happened to anyone else and is there a fix?

I’ve tried deactivating all my plugins and the bug still occurs. I recently created a child theme so maybe it has something to do with that?

Thank you.