If I do that, B items are not updated with A items with same id, B items are updated only with new A items that are not in B

Could you explain what you mean by "updated"?

Items in A array have attributes with updates values. So I need to replace those items in B array, when they have the same id attribute.

.contains()

will check for the equality for all attributes, so you won't match any. You should use

A.forEach { a ->
    if (B.any{ it.id == a.id }) {
        val index = B.rows.indexOfFirst { it.id == a.id }
        B[index] = a
    }
}