What is the biblical basis for elder disqualification?

The Bible speaks to the qualifications of overseers and deacons, and also mentions that they are to be held to a higher standard than the rest of the congregation. What Biblical basis exists, then, for the disqualification of those who are called to shepherd? Specifically, how to these align with the Biblical doctrines of repentance and forgiveness (if, say, a leader was repentant and sought forgiveness over a sin)?