A failing or unscrupulous restaurant will simply not pay its bills. Having an established network of other restaurants you can turn to is the remedy. Chefs can be picky. I thought was of lapidary precision, and he said the leaves were too big. A lot of chefs will call you on quality.
Aesthetics are a big factor for chefs.
I wish more chefs would accept greens with big leaves, but they don't. The way food looks on the plate matters, and you need to understand the plating considerations of each chef. Some chefs will start buying your produce, then find a larger grower who can cut costs and offer better packaging and perhaps even better quality. I had been supplying one restaurant with Asian greens when suddenly a retiree with lots of money hired ten laborers and began growing just for fun. So I moved on.