This seems to be the cause:
The PG is bugged in the first place. It should not be:
butt1 = new BABYLON.GUI.Button.CreateSimpleButton("butt"+i, "");
butt1 = BABYLON.GUI.Button.CreateSimpleButton("butt"+i, "");
Yep, the reason I updated to
this is because it works for subclasses of Buttons as well (ie the FocusableButton added) - updating to use the fix that @Evgeni_Popov suggested is the correct - https://www.babylonjs-playground.com/#VE33T#22
CreateSimpleButton is a static function of Button & shouldn’t use a new constructor.
@Evgeni_Popov had a pull request to change
this back to
Button at one point in Fix static helpers of the Button class by Popov72 · Pull Request #9516 · BabylonJS/Babylon.js · GitHub, but wasn’t landed.