Hey @chrisdb
I also had the exact same problem, and I wonder if you have resolved the issue or not because I managed to resolve the issue for my case. I am not too sure but the cause of the ScrollTrigger position shifting around might be due to poor Cumulative Layout Shift on the page (see here Cumulative Layout Shift). What I have done to resolve it was to set width and height for my images, preload my images in the head element of my html file so the images load in advance to reduce the delay and the layout shifting:
<link rel="preload" as="image" href="image-url" />
P/S: Really cool website you have there, love the design.
