There's no chain of custody when they're mailed to the voter and mailed back. In the May election, there were three problems with them. (1) some people requested them, but didn't get them. Even if they hadn't yet been mailed in, those people had to vote provisional (2) some people thought they could walk in with the absentee ballot on election day or mail it in on election day. The only way they could get it counted would've been to turn it in "downtown" before polls close. (3)nothing to stop mischief such as getting grandma with dementia to request a ballot then fill it in for her.
In OH, they've added so many layers that it's impossible for anyone to follow the whole process. My favorite experience: I went downtown by bus to vote a few days early because I was a poll worker in a different town. I had to show a photo ID plus proof of age to get the Senior bus discount. I got to vote showing a utility bill with my name and address on it!