A mole is the term for a spy that infiltrates an organization and works their way up the hierarchy. Particularly in Comminist countries, where Jehovah’s Witnesses are under ban, it does not sound unreasonable that it occurred.
For the Governing Body to discuss that this happened is not a smart move, as it completely invalidates their claim that appointments are under the direction of the Holy Spirit.
I don’t know of specific cases where this has happened. I know of a number of cases where family members get reinstated, despite not believing it is the truth, simply to talk to relatives. This too shows Holy Spirit does not direct the organization.