Article on Florida VBM rejected ballots. Numbers are low.
I think the biggest category of rejected ballots are those arriving after 7pm election day.
From recent primary: “More than 35,000 mail-in ballots were rejected in Florida primary”
https://www.politico.com/states/florida/story/2020/09/17/more-than-35-000-mail-in-ballots-were-rejected-in-florida-primary-1317327
If I can find the number of rejected VBM from 2016 GE I’ll post. I thought I found that number on Daniel Smith’s site or twitter but a bit fuzzy.