PA in 2016: out of 260,000 absentee/mail-in ballots, 1% (2,548) were rejected.
PA in 2020: out of 2,600,000 absentee/mail-in ballots, just over 1/4 of 1% (968) were rejected.
Math is hard, but there was a 10-fold increase in absentee/mail-in ballots from 2016 to 2020, but an incredible decrease in rejection.