QFileDialog returns wrong path

Recently, I am learning QT. I want to use QFileDialog to open some file. But I don't want to use native dialog, so I set QFileOption::DontUseNativeDialog to true. It works, and I can see QT own QFileDialog.

But there is a problem. If I use native dialog, it will select the first item by default when I enter a folder. But QT own QFileDialog doesn't act the same. Exactly, it works wrong.
Here is the detail.
When I open a QFileDialog, it select nothing, and the open button is disabled.

Then I select a file manully, and the open button is enabled.

Then I enter another folder, but it selects nothing in the folder. What's more the open button is still enabled.

Finally, I click the open button, and I get a file returned. But its path is not correctly. Its path is /tmp/VMwareDnD/config-err-2Emdj0. But the right path should be /tmp/config-err-2Emdj0

What should I do to solve this problem?

My environment.
ubuntu 16.04

https://forum.qt.io/topic/95464/qfiledialog-returns-wrong-path/2

https://bugreports.qt.io/browse/QTBUG-2947