That is indeed the only problem, and it is a hard problem. ASML people like to describe it as "a bit like having robot controlled helicopters tie a rope around

That is indeed the only problem, and it is a hard problem. ASML people like to describe it as "a bit like having robot controlled helicopters tie a rope around a skyscraper in a heavy storm, while not crashing nor pulling the skyscraper over" iirc. This is because at nanoscale, every vibration is a huge movement, and even the flattest surface is mountainous. An ASML machine is basically little more than tons of little sensors and control mechanisms to detect all these vibrations and surface shapes and to adjust the light beam positioning accordingly. Because of this, nearly the entire company (several thousand people R&D staff) is focused on "putting the pieces together". Eg they do comparatively little deep research. It's all engineering.