Citizenship

I hope everyone is doing great. I'm wondering if anyone is in a similar situation as mine and if they have any input. I know have to be patience but i got worried as my interview got rescheduled.
Here is the Description of both ( Cases are in California):

#Note that my filings are based on marriage.Came to US in June 2016. I have 2 pending cases(i-751 & N-400).

#I-751 Case Status#

Case Applied : June 2018
Received extension Letter: July 12. 2018
Bio-Metrics: March 11, 2019
Request Additional Evidence : July 18, 2019
Received Additional Evidence : August 28, 2019

Case is still pending for Answer. I am worried because my GC is going to be expire in Dec 2019 as per extension letter.

#N-400 Naturalization Case status#

Case Applied : May 16, 2019
Schedule Bio-Metrics: May 18, 2019
Bio- Metrics Done: June 5, 2019
Received Interview Letter: August 7, 2019
Interview scheduled: September 9, 2019

But 2 days before interview i got a call from (USCIS FRESNO CA) center where they schedule my interview that they haven't receive my file yet so they are rescheduling my interview and let me know through MAIL as well as i can check online(Online status is still showing "We scheduled your interview"). I cross check about when they will reschedule my interview as per that officer if they receive my file within week it will be in next 35 days. So i am wondering is that normal or happen to anyone else.
As i know N-400 is take upto year to get approved these days and mine went fast within months thats why i am little more worried about it. I already prepared for civics test and was too excited about my interview. Now i still have to wait until get called again. My case is very clean whatever papers they mentioned for I-751 I sent them with some extra proofs of my marriage (Bone fied letter, Mortgage Paper etc.) I applied N-400 online and upload all the proofs they needed.
 
Please Give your replies if anyone have same situation or know anything. I would appericiate your reviews & suggestions.

Thanks.