Is It a Grammar Error?

In our live group classes, I feel like the pronunciation issue or problem that I correct more than anything else is the lack of an S. Almost always the student doesn't even realize they're doing it. It's coming from the accent from their first language. So yes, it can be a grammar issue, right? Because a lot of times students will not conjugate the verb correctly. Subject verb agreement will be wrong. They'll forget that S for, you know, the singular subjects,. Like he walk, she sing, right? They'll forget the S and say that. But what that does mean is that it doesn't, it doesn't affect both your IELTS scores