Q: Bugs on iBooks - PDF name not changing

The problem is that the PDF name in iBooks did not change after I did these two steps:

1. Change the name by tapping on select and then the title of the PDF.

2. Clear the iBooks app in multitasking (the screen after two double clicks of home button)

3. Go back to the iBooks app

After I did these, I found that the title returned back to its original name.

The PDF title would change after these three steps when I was using iOS 9.2.1. It cannot run at iOS 9.3 and iOS 9.3.1.

Does anyone know how to solve this problem? Thank you.