Oh, ok.
The case I found is this.
Whenever I move one citation to another location, the format of the citation does not automatically update according to its position (full format or short format or ibid).
For example:

This is a demo document.
This is from page one one one.1
This is from page two two two.2

1. Alister McGrath, A Theology Reader (Malden: Blackwell, 2000), 111.
2. McGrath, A Theology Reader, 222.

If I move the text:

This is a demo document.
This is from page two two two.1
This is from page one one one.2

1. McGrath, A Theology Reader, 222.
2. Alister McGrath, A Theology Reader (Malden: Blackwell, 2000), 111.


Auto update doesn't happen.
This is the case with "Automatically update citations" enabled or disabled.
Only after I press Refresh, does the format of the citation updated accordingly.

After I press Refresh:

This is a demo document.
This is from page two two two.1
This is from page one one one.2

1. Alister McGrath, A Theology Reader (Malden: Blackwell, 2000), 222.
2. McGrath, A Theology Reader, 111.

I see.
Case closed then.
Thank you for the explanation.