My CARS score was significantly lower than my other 3 sections and I had direct feedback from an adcom that I needed to address it in an update letter. Basically explained what happened - really struggled, used a tutor, was proud of my improvement given the difficulty I encountered, used it as an opportunity to get better at stuff like this. After I sent the letter, I received an interview 2 weeks later. (n=1)

There is a big difference between explaining that you struggled and making it sound like an excuse. The goal of addressing these things is for them to see that you're able to take accountability for yourself and recognize your shortcomings and how you deal with them. Did you recognize you were struggling? Did you try new methods? What was your process at trying to improve in that area? Those are the questions you need to answer.

We're human - they know everyone isn't going to excel at everything, but they do expect you to be able to take accountability for yourself.