Element UI version

2.12.0

OS/Browsers version

Mac OSX 10.12 / Chrome 76.0.3809.132

Vue version

2.6.10

Reproduction Link

https://codepen.io/jerrybendy/pen/eYYBoay?editors=1010

Steps to reproduce

Please refer to the codepen example.

1. Click Monthly button
2. Click the date-range input
3. Click Daily button (Note, DO NOT make the date-range popper invisible)
4. Click the date-range input again
5. Repeat step 1 to 4 few times, the bug would appear.

What is Expected?

The date-range popper should display correctly.

What is actually happening?

The date-range proper shows in a wrong position.

I checked the DOM in inspector, the date-range popper should be mounted under body element. When the bug appears, the popper is mounted under el-input element. this courses the popper shows in a incorrect position.