It is stated that balance virtues and sins of a Prapanna are distributed to others by Perumal before one crosses the holy Viraja. In that case, how do the sins done unintentionally get removed? If another sentient being accrued the virtues of a Prapanna, will this cause delay in attaining Perumal?

Scriptures declare that the merits and sins of a Prapanna go to other persons accordingly. If one had offended a Prapanna, one begets the sins and if one had done good deeds, one is entitled to receive the fortunes. Each one has to exhaust them through undergoing the effects of virtues and sins.
If it is distributed to another Prapanna, he or she will undergo the effects before shedding the mortal coil and this shall not hinder attaining salvation.