I used to get frustrated that my mother would accidentally call me by either of my brothers' names. Then I found myself doing so with my own cats and I forgave her.
Biden has always been a gaffe machine. And hell, even Obama tripped up a few times with things like '57 states'.
The issue, for me, is not the individual incidents, though. It's that people who interact with him, in particular, Congresscritters in his party, publicly speaking out that makes me uneasy about continuing with Biden on the ticket. There is a lack of confidence in his ability going forward; they're better placed to know, and have fewer (not none, but fewer) reasons to lie about it than simple gossipers.