Hi,
But, IMO, you're raising a high threshold for yourself in saying: "The pitot tube operated normally .. as required by its specifications and certifications". The "required" implies IMO that the language in the specs/certifications is strong, some wording that is equivalent to the combination /MUST/MUST NOT/, i.e., mandate the freezing in the conditions of their failure, and mandate the providing of inaccurate information in the condition of their failure.
The language used in certification .. the words used must be accurate and not misleading and should not allow an interpretation that could afford not to keep strictly to these specifications
If this is not the case these certifications are useless and therefore the classification societies and certifications societies (and regulators) must be submitted to an external audit to detect problems .. skills or organizational
Trials and penalties can be at the corner .. as those specifications concern not only technical matters but also human lifes.