I’m not sure why that’ s happening but I noticed something on your site, your images are really heavy… redpla-04.png is over 3 MB, which doesn’t help. You should compress your images with something like Tiny Png and upload them again - https://tinypng.com/.
If that doesn’t help, I think the problem might be related with an interaction. Disable all your interactions and see if the problem persists. If this fixes the issue, start enabling each interaction one by one and testing along the way, so you can see which one is affecting your scrolling.
Hope this helps.
I noticed one more thing, your site is displaying horizontal scrolling. You should fix that - set the overflow of section 2 to hidden.
Cool website, by the way