One thing that was on my mind is the theoretical potential for mail-in ballots to be discarded between being cast and received by election officials. Though this is obviously illegal (it would be considered election tampering as well as destruction of postal property), what if my mail-in ballot was thrown away and it was provable since they never received it because of the post office person throwing them away purposely? How could I cast my vote if possible?
Note: It is common knowledge that mail-in ballots are overwhelmingly Democratic overall since 2020, especially in states that don't automatically mail out ballots, and are Democratic leaning at the local level in most circumstances. So the motive of someone doing this, especially in a competitive state or district is almost certainly to throw away net Democratic votes.