That's what the backups are for. You can have a hung jury but the others can boot one person out. It's happened on a jury my wife was on and then they just brought in the backup and continued as normal
Yeah, even once deliberation starts if it's clear you're just in there not deliberating in good faith they'll tell the judge and they can boot you and assign an alternate.
Might be more than one in there. They ask you all sorts of questions to see if you would be biased, most people would be truthful but there's a certain type of person who doesn't have any qualms about lying and it's the same type that reevers the defendant here.