That’s really the key. How much will this person be able to put up with. And will the others try to get him replaced. There are six alternates.
On the only trial I’ve been on the jury, the alternates were replaced as soon as it went to the jury. If a juror needed to be replaced then it would have required a new trial. I don’t know about longer trials or New York law.
So they can replace a juror that disagrees with the majority?