I'm afraid this will always be the case. Any runtime or VM will have bugs, and the fact there are multiple instance in the world of web development only exacerb

I'm afraid this will always be the case. Any runtime or VM will have bugs, and the fact there are multiple instance in the world of web development only exacerbates this. One day something new may come out, and the web will become a wasteland and web standards will stop being worked on. Then you may finally get a stable consistent target, but alas there will then be no point...