It's sometimes tricky to figure out whether gaffes are signs of an issue or whether it's just the kind of thing that we all do from time to time.
I remember when Bush Jr referred to abolishing the death penalty. He meant to say he wanted to abolish the death tax. No big deal. But when Obama referred to the 57 states you'd think the world had come to an end. Bush misspoke. Obama misspoke. We all do it from time to time.
The trouble with Biden is that he seems to be doing it so often. It's hardly surprising that Republican-leaning sources pick up on every single one and present them as proof, but when even CNN and the New York Times are talking about lists of his gaffes you know there's a serious problem.
From here I'd have expected the Republican-leaning media to increasingly play down Biden's issues and hope he gets locked in as their candidate.