Again, just because a stopped clock can be indicating the correct time, that doesn't mean that it can be relied on to indicate the correct time. You cannot "bootstrap" credibility from an un-credible source just because the un-credible source sometimes repeats the truth. That is just as true whether you assert symbolically (mathematically) or in words. The mathematics, after all, is merely a codification of the words to permit seeing the problem more concisely.
An un-credible source may emit both true and false stories, but because it's un-credible, you cannot draw any conclusion as to the truth or falsehood of any invividual story. For that, you must disregard the un-credible source and go find credible ones.
To do otherwise is the opposite of wisdom.