I wanted to update my blog's dependencies and noticed my playground elements' preview no longer working. Rolling back to 0.18.1 made it functional again.
Reproduced in the demo at https://google.github.io/playground-elements/ with Firefox and Chrome.
Maybe latest on NPM should be rolled back to 0.18.1 so people aren't being upgraded to 0.19.1 by tools such as Dependabot/Renotave or npm-check-updates?