Corrected METARs

[azure]

Late yesterday afternoon at about 2115Z I was mousing around SkyVector looking at METARs in the area and noticed that KMTC was reporting a temperature of 25C. I figured the sensor must have been exposed to the sun or a heat lamp or something, since everywhere else was reporting anywhere from 14 to 17C. Then later in the evening during the Local Forecast on TWC, they announced that Mount Clemens had set a temperature record for the date of 77F. I was laughing at the TWC idiots because the temperature was obviously a bad reading or even a typo, but then I wondered why Selfridge didn't issue a corrected METAR. Well this morning I checked archived METARs for KMTC on ADDS and found this:

KMTC 232055Z COR 18010KT 10SM BKN140 15/08 A2990 RMK SLP137 56015 COR 2057

which I'm sure is for the time in question. I assume "COR 2057" means that the corrected METAR was issued at 2057, only 2 minutes after the reading was taken. So my question is why didn't the corrected METAR quickly replace the original on SkyVector, and how is it that TWC had the erroneous information long enough to log a bogus "record"?

 

[azure]

Interesting that the dew point was slightly different too. I wonder how that happened. I would have thought that they just took a new reading and reported that, but the timestamp is the same as in the original METAR.