Heya, on the awesome weapons demo, the one linked to from babylonjs.com, pressing run causes the error “Cannot delete property 'scene' of #<Window>”. This happens both on version 5 and on version 4.2.
Babylon.js Playground
Removing line 5, which creates a global scene object, fixes the issue for both versions. 
https://www.babylonjs-playground.com/#I6V1ST#209
Yup it is mostly how the PG code has been build so it would fail on subsequent runs.
Could you share where you took the demo link from ? so that we could update it ?
It’s from babylonjs.com, the second demo link in the demos section at the bottom of the page.
Perfect lets check with @PirateJC to update it 
@Blake, thanks for finding this, reporting it, and fixing it!
I’ve fixed the link on the Babylon homepage!
Should be all good now!
Thanks!