Question deleted from question Bank

I added 1 question in a quiz, which is already in another quiz also.
If I delete the question from 2nd quiz, the question get deleted from question bank and another quiz also.

If I check in the same browser its show the question but If I check it in private browsing or another browser then I can see that the question get deleted from everywhere.

Please make your question bank strong and make a different tab for Question bank.
I think it will be very easy for everyone to handle questions if it has different tab.