Thank you!
They give two reasons: (1) they were bullied before, which is a weak argument; and (2) they were promised a full audit for their votes and that promise won't be delivered--a slightly better argument. I have no idea whether they are allowed to rescind their votes once the meeting is over, but my bet is they probably can't any more than a Congressman can, or you or I can. My suspicion is that they know this, and this is empty virtue-signaling to make it up to Republicans.
I've read elsewhere that the Dems on the board are saying it's too late and that the vote has already been certified. Again, I have no idea whether that is true or whether it is reversible.