Thermador documents E12 and E2060 as limescale build-up problems in the heat pump — a direct consequence of hard water rather than a random electronics failure. Running a proper descaling product through a cycle, and adding water-softening salt if your model uses it, is Thermador’s own recommended first step.
If the code returns shortly after a thorough descaling cycle, that points to buildup severe enough to need a technician’s attention rather than a repeat home descaling attempt — worth mentioning your local water hardness when you book, since it helps set expectations for how often this maintenance should really happen.