Our IRB comprises multiple people because we want to get a diversity of opinions represented on the board. So it’s not unexpected to find that not everybody agrees on a particular submission. Votes on motions do not need to be unanimous — motions need only a majority of the vote to pass.
Everyone who has served on the IRB for any amount of time can probably recall some lively discussions on new submissions. The point of a discussion is not to try to persuade everybody to be in agreement about something, because reasonable people can agree to disagree on something. And if a motion is made, and you disagree with some part of it, please don’t feel compelled to vote with the majority just to go along with the crowd. It’s fine to dissent on a vote. Even if we ask you to explain your vote, it’s not because we want to single you out — it’s just so we can ensure our minutes accurately reflect the “controverted issues and their resolution” we’re required by regulation (45 CFR 46.115(a)(2), if you don’t believe us) to document.