In Time Matters (free eBook, also available on Google and Amazon) we discussed that Einstein was originally right about our Universe being static, not expanding. But later, under peer pressure, both from the Academia and the Church, he changed his mind to the expanding Universe, and even recognized his original position as his biggest blunder.
Another interesting example of Einstein’s disagreement even with nowadays mainstream, is about Black Holes and the surrounding them Event Horizon: Einstein was confident (just by physical principles) that Event Horizon is just a math blunder, and he was right again.