Persistent and consistent coaching of the Person of Peace or another inside leader of a Discovery Group is the way DBSs avoid heresy. It is instructive to realize that 1 Corinthians and 2 Corinthians were letters Paul wrote to a group of believers in Corinth. Clearly that church had its struggles with false teaching and false practices. The founder, Paul an Apostle, did not stay with that young church indefinitely. But he had ongoing relationships with some of the people there and those insiders kept him informed.
Ongoing relationships with key leaders of a family or friendship group are critical to coaching a Discovery Group toward faith, becoming a church and guiding them to plant additional generations of churches. Early DMM trainers used the acronym M.A.W.L. as Model, Assist Watch and Leave. More recently some have changed the L to Launch. Leaving never referred to Leaving Alone.
The good catalyst recognizes the longer he/she is a personal participant in a Discovery Group, the greater the risk that the Group will develop a stunting dependency upon her/him. The goal is to model good Discovery. Assist an inside leader (someone the family or friendship group already looks upon as a leader) to be a good facilitator and then Launch that person into the role.
Weekly meetings with this Inside Leader provide opportunities to identify problems which are arising, recognize theological errors which may be surfacing and coach this leader to healthy corrective studies and practices. Personal presence is not the only way to bring correction, otherwise Paul would have dropped everything to return to Corinth. It is very possible for an Outside leader to stay too long and cause far greater problems than arise when he/she leaves too soon.
Also, we must recognize that the Discovery process has been developed to ensure that the actual teacher is the Holy Spirit at work through the Word of God which is being explored in each gathering. How much do we really trust the Holy Spirit? Are we more confident in our abilities or the power of the revelation of God contained in Scriptures?