Citizenship Interview - 2nd time


Registered Users (C)
I applied for citizenship 3 years ago, and had an interview on 3/24/21, interview went fairly ok, I passed the tests, and answered other questions, but the IO told me that they need time and will write to me. After 120 days of first interview, they sent notice for 2nd interview on 8/17/21.

May I know what would be the reasons for 2nd interview? How to prepare for that? Interview notice does not say any.

I have NO criminal history and was never arrested. I always paid and filed taxes on time.

July 30, 2018 - submitted N400 online, after 5 years of GC.
August 20, 2020 - USCIS responded to the congressional inquiry saying they are waiting for background checks.

March 24, 2021 - Interview at San Francisco office, following were marked on form N-652
You passed the English test and the US history and government test.
USCIS will send you a written decision about your application.
A decision cannot be made yet about your application.

August 2, 2021 - scheduled 2nd interview for Aug 17, 2021.