In listening to Bannon, it was talked about how the mail-in drop-off box broke chain of custody. So, no ballots coming from those boxes have any guarantee of chain of custody due to the transport.
During transit, there is no need to open mail-in ballot. You just a count, say 3000 ballots. Simply replace those 3000 ballots, in transit, with 3000 of fake Biden ballots. Drop off those fake ballots, and destroy the original 3000 from the ballot box.
Rinse and repeat.
No need to even count. Just have some in the box. You can swap envelopes later. So what if you are 100 short.
Keep the envelopes.