Most interviews are decided well before they finish, and the candidate is usually the last to know. The remaining questions get asked out of politeness.
The moments that cause it are less dramatic than people expect. They are rarely a wrong answer to a technical question.
Criticising a previous employer
The most reliable one. However justified the complaint, the interviewer cannot verify it and has only one data point: you are someone who discusses former employers this way. They will assume they are next.
The workable version describes the situation without the verdict — what the constraint was, what you did about it, what you would want to be different. Same facts, no character judgement.
Not having a question
'No, I think you've covered everything' reads as indifference, whatever it means. It is also a wasted opportunity, because the questions a candidate asks are one of the few signals interviewers weight heavily.
Two prepared questions about how the role is actually judged — what a good first six months looks like, what the previous holder found hardest — carry more weight than most rehearsed answers.
Being unclear about why you are leaving
Vagueness here is read as concealment, even when the truth is mundane. A plain reason, briefly given, closes the topic. An evasive one keeps it open for the rest of the conversation.
Answering a different question
Candidates who have over-prepared often steer every question back to their strongest anecdote. Interviewers notice, and it reads as either not listening or not having a second example.
Answering the question that was asked — even briefly, even with 'I haven't hit that exactly, but the closest was' — lands better than redirecting to safer ground.