@Jerseybigfoot: unfortunately I don't know what will happen there, as soon as I have news I will post something.
@djmercer: interesting question. I needed to think this through before giving you an answer.
From what you describe it sounds almost impossible to have had under readings: your zero offset was lower when you zero-d in the morning, when it was presumably cooler then when you normally zero. The Type S is very well behaved in terms of temperature and is pretty flat in the "typical" temperature ranges.
The thing is - a lower zero offset leads to higher readings, because the current torque value is (current value minus zero offset). The power meter also re-zeros every time you coast more than 2 seconds (provided you stop pedaling and don't turn the legs), so if your race way "normal" it will have re-zeroed a number of times during the race, which would have eliminated any wrong zero offset, and should have realigned the power to effort relationship. You should then have seen a big jump in numbers.
A question for you: how often have you raced at the target wattage levels to date? I am asking because personally the wattage I can achieve varies quite a bit depending on the day. For example, this april I did a 70.3 simulation at the end of the training camp and was about 15w higher than in a race I did 2 weeks later when I had tapered. Similarly on a long sportive ride this weekend, where I performed less strongly than at altitude in Boulder when I felt bad and was tired (note: I verified the data on steep climbs).
So I wouldn't exclude the possibility that it was a bad day, based on the fact that what you describe with the zero offset doesn't offer a plausible scenario leading to under reading. In my racing I try to take power, HR and RPE into account and act accordingly. When I am fresh and well tapered and the target wattage feels too easy I take it as a cap. On days where I can't hold the target wattage I don't force myself to hold the watts but let RPE and HR take precedence.
I hope this helps.
official power meter of Movistar Team