Our production facility is having some problems filling orders on time. At first, they were only having difficulties with highly customized orders. But now things have got worse, and even run-of-the-mill (08/15) orders are often delayed. I think some changes need to be made urgently.
This idiom is American in origin, and seems to come from the late nineteenth century. The mill was a weaving mill and the first articles called run of the mill were clothes – they came directly from the mill with no added decorations. And from this, run of the mill came to stand for something ordinary and basic.