How do you know if a sequencer is bad?

So, how do we determine if a sequencer is faulty? What are the telltale signs that indicate it's not performing up to par? Are there any specific diagnostic tests we can run to pinpoint the issue? And if we do find that the sequencer is indeed bad, what are the steps we should take to replace or repair it? I'm eager to learn more about this process and how to handle it effectively.