ReorderablelList don't refresh immediately after change order.

I found when I change array element's order, it won`t be refresh until I click other window.

Screen capture is below.
As you can see, I change element's order, but it keeps change back. It suddenly refresh after I click other window. Such as click Hierarchy and click back or click scene view window.
It won`t work when I use ReorderablelList inside Editor Window, too.

I test in 2020.2.2f1 and 2021.1.0a6.
The project is new and empty. So I don't know why this keep happening.
Thanks for help.