I had a couple bad experiences doing restaurant shops, so I pretty much avoid them.
The one that still bothers me more than a year later was a quick service restaurant (like Denny's or IHOP). The instructions clearly said to hold them to a four star restaurant level. In big red capital letters, so I did. The instructions said I had to take a guest, so I took my son. And it gave detailed instructions on what to order, and we ordered those things exactly the way they said to do it. The waiter, for some reason, singled me out, he didn't figure out that I was a shopper, but he apparently decided that I was bad and he was going to make me miserable for the rest of my visit.
When I reported that the food was cooked incorrectly and most or all of it was not fresh, all of it was canned, overcooked or mushy, gray and disgusting. The editor said I should cut them some slack, because they are not a fine dining restaurant, and they wanted me to change my report. Maybe I shouldn't have refused, but I felt I was following the instructions I was given. The editor told me that I shouldn't bring attention to myself, but I did not try to bring attention to myself, the waiter and his manager were mean to me and I don't know what I did to cause it. I never asked for anything special or extra that I wasn't instructed to ask for in the directions. I didn't complain about the food out loud (I also didn't eat very much of it because it was gross). But in the end, the MSC refused to accept my report, and they banned me forever, and cancelled all of the shops I had scheduled because I followed their instructions and they didn't like my answers.