Clear or reset Decentraland's UIContainerRect

Question

I created a custom UICreator class with the attribute lowerContainer that contains a button and I'm trying to remove it to put a new one, but the new button appears whithout remove the first one.

I tried to recreate the whole UI and also reset the button container, but the first button is still there. This is a simplified version of my code:

// Contants.ts
export class Globals {
    static readonly CANVAS = new UICanvas()
}

// UICreator.ts
import { Globals } from "Constants"
export class UICreator
{
   lowerContainer: UIContainerRect

    constructor()
    {
        this.lowerContainer = new UIContainerRect(Global.CANVAS)
        this.lowerContainer.width   = "100%"
        this.lowerContainer.height  = "15%"
        this.lowerContainer.hAlign  = "center"
        this.lowerContainer.vAlign  = "bottom"
        this.lowerContainer.visible = true
    }

    addButton(label: string)
    {
        let btn = new UIImage(this.lowerContainer, new Texture('assets/btn.png')

        let btnLabel = new UIText(btn)
        btnLabel.value = label ?? 'no-label?'
    }
}

// game.ts
const ui = new UICreator // create and show my UI
ui.addButton('Continue') // add a button
ui.lowerContainer = new UIContainerRect(Global.CANVAS)  // "Reset" the UIContainer
ui.addButton('Finish') // add a new button

And this is how it looks: As you can see, the 'Continue' button is still there.

I checked the UIImage, UIText and UIContainer properties and methods looking for some kind of "self destroy" or "reset" functionality. I'm new with Decentraland and with Typescript, so I assume that I'm missing something.