A partial response here:
https://publiclawforeveryone.com/2022/09/02/legal-opinion-on-the-privileges-committees-partygate-inquiry-some-comments/
I'd particularly like to draw attention to the part of my link above where Mark Elliott writes:
// A statement that unintentionally misleads the House, and which should not therefore be regarded as a contempt at the time of its utterance, may become a contempt should the Member in question later become aware of its falsity and fail to correct the record. The notion that the record must be corrected in such circumstances is uncontroversial ... //
As the Ministerial Code says, "...it is of paramount importance that Ministers give accurate and truthful information to Parliament, correcting any inadvertent error at the earliest opportunity."
In this case, Johnson stated unequivocally, on several occasions, that there were no parties in Downing Street during Lockdown, or that such parties as there were broke no rules. I will happily accept that Johnson was sincere in believing this at the time that he said it. Still, it was wrong. And it seems a stretch to argue that only the preliminary release of the Sue Grey report was "the earliest opportunity" to correct the record.
As a separate matter, it is not Harman who has "mov[ed]the goalposts" -- the suggestion that intent is not relevant comes straight from a literal reading of Erskine May, which holds that merely if the "act or omission ... obstructs or impedes either House of Parliament in the performance of its functions", then it may be said to be contempt, and there is no mention of intent in that paragraph. Anyone who makes a genuine mistake should of course be, and always is, given an opportunity to correct the record. Hence why Erskine May goes on to say that "many acts which might be considered to be contempts are either overlooked by the House or resolved informally".
The question the Privileges Committee is then asking isn't narrowly about whether what Johnson initially said was misleading -- which is a good thing, because it clearly was, since he was wrong -- but rather a wider question, about what followed that initial (wrong) statement. Did Johnson correct the record at the earliest opportunity? If not, why not? Nor is this meant to be in the literal sense of the very next time he was in Parliament. In other words, the contempt wouldn't be due to being wrong in the first place, but in allowing the error to persist for longer than it could have.
The closing part of Mark Elliott's link is also interesting. Ultimately, the Privileges Committee process is one of the clearest possible examples of a "Proceeding in Parliament", that judges and Courts therefore cannot question. It's therefore simply wrong to apply legal standards to the Committee's work. I suspect that Lord Pannick knows this.