I tried to build and preview the minimal demo and the problem is the same (see the video). I had to slow down the loading using throttling so I can see it more often. So I added ScrollTrigger.clearScrollMemory(); to the top of the page and it is working fine! 🎉 So thank you for help @Rodrigo
// prevent scroll jump problem on reload
import { gsap } from 'gsap/dist/gsap';
import { ScrollTrigger } from 'gsap/dist/ScrollTrigger';
ScrollTrigger.clearScrollMemory();
svelte2.mp4
Pavel Stianko's post in Scrolltrigger on reload problem (Sveltekit) was marked as the answer