I work in a lab. We can't use our most accurate scales when there's construction going on with heavy machinery within a couple of blocks. This isn't cutting-edge stuff either, it's measuring to 0.001 gram, with a $10k scale and a 4" thick granite table on rubber pads (unlike other equipment that's on air floating supports with active counter balancing).
That's so interesting, thanks for sharing!
Heavy equipment causes vibrations in the ground, which most people probably can't notice, but when you're literally printing at the atomic scale, microscopic vibrations probably make a difference.