Classical architectures often have difficulties at this level. A developer writes new code and unintentionally introduces a new dependency between two modules, which had been forbidden in the architecture.

Typically, the mistake goes unnoticed because attention is only paid to the code level of the system and not to the architectural level.

Often, it is not immediately clear which module a class belongs to. So it is also unclear to which module the developer just introduced a dependency.

In this manner, more and more dependencies are introduced over time. The originally designed architecture becomes more violated, culminating in a completely unstructured system.