What the majority decision says, which is asserted by four of the seven justices, is that if there's an irregularity that affects the result of the election, those votes will not be counted. However, the important part of their decision is that not every error counts as an irregularity. That's something that is often missed when people try to summarize what happened in that case.
For example, concerning the vouching errors, whereby the vouchers' names were not listed, in that particular case the Supreme Court majority said that those kinds of errors do not amount to an irregularity. Likewise, the registration certificates were lost; 16 of them went missing. Once again the Supreme Court—