Do you use Stripe's risk evaluation API? In my experience, a lot of chargebacks come from people who have had their credit card info stolen, then file a chargeback when they see the unknown transactions in their statement.
You could also try using the two step auth and capture method to allow more time for the victim to realize their info was stolen and do an additional fraud check with potentially more up-to-date models right before performing the capture.
I haven't used CreditKarma's tax product either so I can't speak to its accuracy, but from my understanding they didn't build their own product, they acquired a company called AFJC which has been in the online tax space for a while.
That quote reminded me of something my mentor told me when I was training to interview people in-person. He said if they're really struggling, change it up with an easy question for exactly the reason you gave, but also to get their confidence up so they don't start the next interview feeling bad.
To add to your second point, it's also good to make people come to you if they need anything from someone on your team so you can filter out all the unnecessary interruptions and let them focus on their work.
You could also try using the two step auth and capture method to allow more time for the victim to realize their info was stolen and do an additional fraud check with potentially more up-to-date models right before performing the capture.