Demo gives an error sometimes (works acress page reloads)

[nlzet]

On my first request it didn't work, I noticed it did work across multiple page reloads.

When it doesn't work I see the error: TypeError: window.customElements is undefined - img-2.js:365:1

(Browser: Firefox 59.0.2 / 60.0b14 developer)

[RevillWeb]

Thanks for submitting this, I'll investigate, maybe the Custom Elements polyfill isn't getting loaded correctly.