I'd worked in similar roles for about 5 years prior, but I didn't have any formal qualifications in the field, I'd just learnt along the way. The interviewer handed me a cereal bar in its packaging that he'd been holding and asked me what was wrong with it. I'd put on my CV that I'd done artwork checks which was true, but I was only looking for really obvious things like typos. I was getting really stressed because I couldn't find the mistake whilst he was staring at me and I guessed something about the picture because it had a raspberry picture on, but the ingredients list said raspberry flavour so I thought maybe that was it, but no. The answer was something I wasn't aware of about sugar regulations and he seemed to find it quite amusing that I didn't know, and started to question my CV as if if lied. I'd only ever been in "assistant" roles, everywhere else I worked employed someone who was paid a lot more than me to make the big decisions. He started asking me more really specific questions about certain regulations and I just didn't know the answers. By the end I had tears in my eyes because he was ripping into my career history and telling me that I didn't know as much as I thought I did. I had never claimed to know the specific things I was being asked about. Very disheartening experience.