I used the old version of NOC codes when I applied. My NOC for RA/TA was 4122.
My TA duties was Conducting undergraduate laboratory, Leading tutorials, Grading lab assignments, Marking mid-term and final exams. They actually accepted my TA duties.
My RA was Conducting and Studying ...... in the field of ..... . They disagreed with my RA duties and rejected me because it didn't match the NOC duties.
I also claimed the previous work experience in my back home. I couldn't find the exact NOC match with my career. However, I used the nearest NOC to my work experience. They didn't accept my previous work experience as it didn't match the NOC code.
I don't know how the CIC officers think about the PhD students. Why we need to exactly provide the letter that describes the RA duties of a PhD students like what they mention in NOC duties. OK, We just go to university and watch soccer and play game and check Facebook. Even my grandmother knows what I am doing in the lab. It is clear. we do research, conduct literature review, prepare lab equipment, ..... The CIC officers are all douche bag.