In my case this was caused by images using lazy loading, thus only loading when in view.

This fixed it for me, add this to the bottom of the script.

let resizeTimeout;

function refreshLenis() {
  clearTimeout(resizeTimeout); // Cancel previous resize calls
  resizeTimeout = setTimeout(() => {
    requestAnimationFrame(() => {
      lenis.resize(); // Recalculate dimensions inside requestAnimationFrame for smoother transitions
    });
  }, 300); // Adjust delay as needed
}

// Refresh Lenis when the page fully loads
window.addEventListener("load", refreshLenis);

// Also refresh Lenis when lazy-loaded images finish loading
document.querySelectorAll("img[loading='lazy']").forEach((img) => {
  img.addEventListener("load", refreshLenis);
});