One of my peeves with control theory, at last the way it's used by proponents I've met, is that it's designed to react to the smallest input. This makes intuitive sense when trying to optimise performance, but in a system with natural variations around the mean (noise), this can easily lead to amplifying variation and worsening performance.
The alternative is statistical process control. In practise, it performs about the same for basic tasks, but it gives you qualitative insights into many other things too: (registration-walled) https://www.qualitydigest.com/inside/operations-column/proce...