Hello Yongki,
From your description, it is difficult to determine what might be the cause. I am unable to reproduce the issue. More details are needed.
1) Is the issue only reproducible for this particular project or does it occur also for other projects? What about the example projects included with the RTD SDK? What about a newly created project from the New Project Wizard?
2) If this issue can happen on an example project or a new project, what steps must be followed to create the issue?
3) If the issue only occurs on your project, could you share the project with us so we could try to reproduce the issue on our side and investigate the cause?
Best Regards,
Mike