I refer to this recent question:
Recently, during a parish Reconciliation service, the priest advised all present to limit their confession to no more than two mortal sins. He then advised the same penance for all and dismissed us to go to one of the “confessionals.” Is it within a parish priests competence to limit full confession and still have a valid Reconciliation?
The answer given by Fr Serpa was that this the priest has no authority to do this, however that leaves the question of whether the penitents who confessed in good faith as instructed, and omitted one or mortal sins, are obliged to re-confess?
This is certainly not a hypothetical question, as this and similar, abuses of the confessional do occur.
If the penitents are obliged to re-confess, is such binding under pain of sin? Obviously those who are a unaware of the obligation commit no sin, however, once they become aware of it, would it be a sin to not re-confess?