Blind spot 1: Immiseration
According to Lakatos, Marxism predicted “the absolute impoverishment of the working class,” which didn’t happen. Marxists didn’t admit the mistake, kludged up some excuse, and moved on. See the previous post.
I think the story is more complicated, and it’s an example of how critical rationalists think experiments (natural or otherwise) and theories are way simpler than they actually are. As a result, their methodology (rule book) for science misleads.