IRB votes don’t have to be unanimous, or even close to unanimous. Reasonable people can have differing valid viewpoints, and there’s no need to wait until it looks as though everybody agrees on whatever’s being discussed to make a motion. If you are getting the sense during the meeting that further discussion would do nothing to change anybody’s mind, it’s OK to go ahead and put forth a motion. If someone is willing to second it, the motion can be voted upon, with the results recorded in the minutes. Divided votes in fact help document that the IRB membership reflects a diversity of viewpoints and that members feel comfortable expressing those differing views.