The ripple effect on the buttons is not working. For every click on a button, the span.md-ripple-wave is added, but never removed, and there is no ripple effect. It also doens't work in your own example:

https://codesandbox.io/s/github/vuematerial/examples/tree/master/examples/login

Reproduce:

1. Go to https://codesandbox.io/s/github/vuematerial/examples/tree/master/examples/login
2. Click on the login button, no ripple effect.
3. You can also see in inspect element that a span element is added on every click, and never removed

I tested this in chrome and firefox on Linux, both have the same issue