> They don't calculate the difficulty correctly? Yes. It's possible to create a long chain at low difficulty and the original bitcoin client protects against t

> They don't calculate the difficulty correctly? Yes. It's possible to create a long chain at low difficulty and the original bitcoin client protects against that by computing the total "work" that has gone in a chain. However, Electrum just assumes that the longest chain will be the one which has most "work" in it which is wrong.