Being told: "no problem" every time I ask for something. "can I have more coffee"? No problem. "can we have our dessert to share"? No problem. "thank you for taking care of us"? No problem.   If it seemed like a problem, I probably wouldn't even ask you. Answering "no problem" infers it may have been a problem, but right now it's not a problem.   Serving customers' meals should never infer there's any kind of problem!