Did your father were asked specific questions during the interview or merely his documents were verified, because I am a senior applicant that waiting for the interview letter .Some officers are grumpy and in order to assert their authority making things complicated and delaying things. My fathers is 80+ and the ofiicer told him that some seniors do not become citizen as during the oath ceremony they are not able to repeat the oath after the judge. I told that I will practice with him before the ceremony and she said he must be able to understand what the judge is saying and repeat after him. My father speaks good English but he has issues understanding different English accents and of course age is a factor as well and he does not pick up things fast and his hearing problem makes thing more complicated.
Thanks in advance.