Failure does not disqualify disciple-makers if there is genuine repentance.

Restored disciples can become shepherds of others. Peter denied Jesus three times, even though Jesus had warned him it would happen. Thankfully he repented. This was in contrast to Judas who also failed but chose suicide instead of repentance. Jesus forgave Peter and restored him, not only to relationship with Himself, but renewed his calling and gave him important responsibility of shepherding others.