This is not a hidden defect, but obvious. ...
If the seller tried to conceal a defect by simply plastering over and painting, it would be deception and thus potentially liable for damages. However, no deception is present here, since the damage was not concealed. Nevertheless, I would have it—and any (!) other irregularities—recorded in the protocol.
The following can be found on the internet (link is not allowed):
"...
Important: The clause “Bought as seen” does
not constitute a
complete exclusion of warranty! When a house, apartment, or property is “bought as seen,” only the warranty for
obvious defects is excluded.
» The seller is therefore not liable for defects that an average buyer could have noticed during a thorough inspection of the property without an expert. Whether the buyer actually inspected the property for obvious defects does not matter. The clause “Bought as seen” does not cover
hidden defects, however. Hidden defects exist when an average buyer cannot detect the defect through their own inspection.
» Note: In the case of hidden defects, the buyer can therefore rely on all
warranty rights. The prerequisite, however, is that no general warranty exclusion was agreed upon in the contract!
2. Examples of obvious and hidden defects Obvious defects exist, for example, in the following cases:
» Peeling plaster and visible cracks in the facade.
» No running water due to defective pipes.
» Aircraft noise and other noise nuisances (for example from streets, shops, and venues).
» Doors and windows that do not close properly.
» Leaky roof due to larger holes.
» Mold on walls and ceilings, provided it has not been freshly painted over or “hidden” by a wardrobe.
The following examples, on the other hand, are
hidden defects:
» Contaminated sites on the property.
» Asbestos in the building.
» Leaking gas pipes.
» Use of health-damaging wood preservatives.
» Rusted, non-visible steel beams.
» Non-professional insulation of the attic, provided this can only be detected by an expert.
..."