Notes App cannot close PDF files after LockTask

I use Galaxy Tab A9+ SM-X210 to develop Kiosk for company. First, the Samsung Notes App is preset as the PDF opening tool. After entering LockTask, the PDF file can be opened normally for reading, but there is no response when clicking the return key on the Toolbar. After releasing the LockTask, it will operate normally.

How should I solve this problem?

Hello

Please create a support ticket in the Samsung developer support channel.