"Trouble" on a batch plant is anything that slows down production or delivery or degrades the quality of the concrete being produced. Trouble comes in several forms: product quality problems, production speed problems, accuracy problems, and reliability problems.
Whenever things are going fine and then suddenly go sour for no explicable reason, there is usually a critical piece of the puzzle missing. Whenever things don't add up, go over everything, no matter how unrelated, that took place just before the breakdown or problem. The answer will usually be obvious.
The first step in a systematic approach is to isolate and identify problem sources. Unless you know what is normal at every point in the process, you can't begin to isolate, much less identify, what is wrong. This technique is called benchmarking. Without regular performance measurements, subtle problems can take root and grow so gradually they are not noticed unless they are compared to peak performance measurements.
Another effective approach is to logically whittle the problem down to size. This is a highly efficient troubleshooting technique. Every time you subdivide the problem into two parts--1) the part without the problem and 2) the part with the problem--the part with the problem gets smaller and smaller, and takes less time to troubleshoot.