Scroll the mouse and you will find the button disappears
That’s an interesting case that we should check, of course. Ot os probably due to children-clipping because of the way you define the “top” variable.
But There is a better, more well-structured solution:
Scroll Viewer Example with Grid of Images | Babylon.js Playground (babylonjs.com)
We have a stack panel element that takes care of stacking different elements on top of each other (very much what you are trying to achieve), without manipulationg the “top” variable, adding more for each button.
I’ll see with @carolhmj if she has the time to check the issue