Unable to delete slash from str in EditText date formatter

I have a date formatter that takes in String input from a text field. It formats correctly. However, I am unable to delete the first "/" it keeps 3 strings in UI when using the keyboard delete. I am able to delete the second "/". Any idea why this is happening?

internal class DateFormatter {

    override fun format(input: String): String {
        val cleanInput = input.replace("/", "")
        val textLength = cleanInput.length

        var result = ""
        result = if (textLength >= 2 && textLength < 4) {
            cleanInput.substring(0, 2) + "/" + cleanInput.substring(2)
        } else if (textLength >= 5) {
            (
                cleanInput.substring(0, 2) +
                    "/" + cleanInput.substring(2, 4) + "/" +
                    cleanInput.substring(4)
                ).take(10)
        } else if (input.last() == '/') {
            input.substring(0, input.length - 1)
        } else {
            input
        }

        return result
    }
}