I'm not a lawyer, but I don't think this can be right. Many appeals succeed on the basis that the judge misdirected the jury, and we don't see a queue of unemployed judges stretching down the Strand.
And as for "may be illegal" -- that applies to the outcome of very many complex cases.
I think judges only have to resign over serious matters of integrity or impropriety -- taking bribes, being more than averagely senile, or doing unspeakable things to small animals. Oh, no, the last is still allowed, for the moment....