component seems to be destroyed incorrectly

Version

3.0.1

Reproduction link

https://codesandbox.io/s/zx88kqjzj4

Steps to reproduce

• Enter pageA.
• Click "pageB" to enter pageB .
• Click "pageC" to enter pageC from pageB.
• Click "pageA and pageB", then back to pageB.
• It's back to pageA, but the URL bar show it's in pageB.

What is expected?

back to pageA correctly

What is actually happening?

I can not back to pageB, and the pageA component seems to be destroyed.

---

...I'm not sure that the problem is caused by vue-router. Maybe it's caused by keep-alive component.