Well, i could make a demo, but it doesn show the issue.
The main thing is, when i remove a scrollsmoother plugin from my website, everything works fine, nothing jump, and when i click the link, scroll stays at the same position of the page, but as soon as i turn on scrollsmoother, i face this issue.
May be you can figure our what is going on just by clicking that link in the footer section. You will see that scroll goes to beginning of the page, and turns back to footer