Your students are forming a mental model of how something works. Your job is to help guide them to the correct mental model.

If their mental model goes wrong, you have to debug it: you need to figure out exactly what they've misunderstood (which could be anything, and could be from years before your lessons with them started) and help them correct.

Here's a really good detailed write-up of this idea: https://teachtogether.tech/en/index.html#s:models