Powers of the Secretary of the Grand Chamber of the Supreme Court after the expiration of the term

I read that in the Grand Chamber of the Supreme Court, the three-year term of a judge as Secretary has ended, and judges are electing a new one. I am curious, if the judge's term in the Grand Chamber has ended, does he still have any powers as Secretary until a new one is elected, or does everything cease automatically? How is the continuous work of the Chamber ensured during this transitional period?