Strong claims need strong evidence. So the choices are between:

a) oops, they accidentally blocked ONLY left-wing political candidates and causes right before an election, ever since the US started having a right-wing president with a track record of interfering in elections on behalf of right-wing causes, totally a coincidence, people, or

b) yet another example in a facebook's history of blocking left-wing political candidates and causes, right before an election, ever since the US started having a right-wing president with a track record of interfering in elections on behalf of right-wing causes

Obviously Facebook does not have the benefit of the doubt, given their long history of malfeasance, deception, and nontransparency, so A is a pretty strong claim, and thus we can go with B until you have strong evidence otherwise. I don't think anyone here on HN can say "I trust facebook to be honest and transparent, to admit, explain, and atone for their malfeasance without prompting, and to always make choices that best reflect the will of the people" with a straight face these days. In fact, we still don't even have transparency into the very incidents we're discussing (likely due to deception and malfeasance, if we're going based off past behavior and proper Bayesian priors).

Indeed, if it was actually an accident, then that means that after Facebook's Lula scandal, they had the opportunity to stop this sort of thing from happening, and made the choice not to do so. That was their choice, making it no longer an accident in this case. There's no escaping accountability for that choice.

Back to our earlier request: can you give some examples from the last couple years, of Facebook blocking major right-wing candidates or major right-wing mainstream political movements, immediately before an election? If it was just an accident, and these accidents happen all the time without respect for politics, we should expect to see an equal number of blocks applied to both sides in the same situation. Do we? I don't think so.