Not suir
Not surprising. One clue to how frequent such things will be can be seen in the words being used by apologists for universal mail-in balloting these days.
Formerly, the claim was that there has been no vote fraud. Now, however, after many instances of it have been discovered, they are saying "there is no evidence of massive voter fraud."
Well, with a statement like that, no amount of fraud can disprove the claim since "massive" can be expanded to mean almost anything!
In case anyone has not noticed this "adjustment" in responses given to the proven instances of voter fraud, pay attention to the discussions on TV or elsewhere as this topic continues to be a "hot" one.
And, by the way also, that is only about voter fraud. What the Original Post here brought to our attention might be dismissed as one small case of a simple foul-up in the routing of ballots or applications.
There have been literally MILLIONS of such ballots going astray, which in itself is reason for not trading our relatively safe system of voting--along with reasonable provisions for people who absolutely cannot get to the polls on election day--for a system that makes error and fraud much more likely.