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Interesting. Would the 13-microsecond discrepancy mean that GPS positions were over two miles off during those 12 hours?

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No, the discrepancy was only on a timing message for determining UTC. This is not used for determining position.

Specifically, one or few of the sattelites sent a wrong value "A0" in its "Page 18 of subframe 4" message. Page 37, §2.4.5.5 in http://www.gps.gov/technical/ps/1995-SPS-signal-specificatio...

https://www.febo.com/pipermail/time-nuts/2016-January/095692...

Probably not if they were all off by the same amount.

Position is based on relative difference between time signals received from different satellites, not absolute.

This error only occurred on a certain revision of GPS satellites, not all of them. It would have been a problem, except luckily the error was only on a message for determining UTC. The error did not affect the message or clock that are used in determining position.

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