It is not uncommon for applicants to have a differing account of what transpired during a visa interview or a port of entry matter from what an immigration officer says occurred.
The Federal Court recently dealt with the matter in Gedara v. Canada (Citizenship and Immigration), 2016 FC 209. The Federal Court stated:
The affidavits filed by the Applicant and by the Interviewing Officer present opposing accounts of the tone of the interview and whether concerns were specifically communicated. I find the Applicant’s affidavit more persuasive and assign it more weight for the following reasons.
I agree with the reasoning in Rukmangathan, above, at paras 30, 31, citing Parveen v Canada (Minister of Citizenship and Immigration),  FCJ No 660 (Fed TD) [Parveen], that “…[v]isa officers deal with many applications, one can expect that they will not have as precise a memory of the event as does the applicant” (Parveen, at para 10). The interview took place on March 11, 2015, yet the Officer’s affidavit was sworn in December 4, 2015 – approximately nine months later. The extended passage of time and the number of interviews this Officer would have conducted in the interim calls into question the reliability of her attested statements made months later.
As well, the Officer’s affidavit essentially reiterates the GCMS notes, adding very little to their substance.
In Rukmangathan v. Canada (Minister of Citizenship and Immigration), 2004 FC 284, the Federal Court stated at paragraph 31 that:
Here, the memory of the visa officer has been placed in doubt, given that she has attested to writing the notes at the time of the interview, when clearly she wrote them close to a month past that time. The events of the interview cannot be said to have occurred precisely as the officer has attested to them. Further, her account of the interview is vulnerable due to the fact that she failed to record her impressions of it during the interview, or closely thereafter.
We have successfully litigated matters where our client took detailed notes contemporaneously with an event while the immigration officer (or ESDC and CBSA, as they were in our cases) did not, or the notes were not as detailed, and typically recommend as a result that our clients always take notes of what transpires.