There's no way to tell, given just this information, whether the MT is faulty or not. I would try moving some of your MT11s around, if you can and see how things change (or not) between sensor and environment. In particular, if you have another one providing the kind of values you expect, could you deploy it, for a short time, alongside the existing one, to see how their results compare? I've found that humidity changes quite a lot, in relatively short periods of time, in some environments.
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