you serious issue IS merged https://github.com/webcomponents/webcomponentsjs/pull/644 ;-)
Also its NOT polymer issue - it is polyfill issue. It affects things like x-tag,bosonic and others. ANyways it looks like latest release is the fixed version.
Also its NOT polymer issue - it is polyfill issue. It affects things like x-tag,bosonic and others. ANyways it looks like latest release is the fixed version.