I called Porsche customer service, and was told that this is a global problem with car connect, and that their tech team is aware of this problem and are working on it. They didn’t provide a forecasted date when they expect it to be corrected, nor did they know how they would notify us when (and IF) it is fixed.
I've had the same issue for the past week or so. 9,144 miles on the car odometer displays in the PCC app as 5,681 miles. Definitely not correct, but other than that everything looks ok, including the miles remains until empty.
As an experiment, I went into the PCM and changed my speed display units to km/h. Now my car odometer reads 14,716 km, and the same number on the PCC app. When I switch back to mph, the issue returns, which made me suspect a conversion error.
Using an online unit converter, I input the 5681 miles (incorrectly displayed in the PCC) and converted it to km/h, I get the correct number of 9,144. My guess is that the conversion between units is done in the incorrect manner. Their system thinks my car's 9,144 miles is in km, so converts it to mph for the PCC app display. I wonder if this issue is only being seen by those of us that use mph, not km/h.
As long as my car is correct, I guess I don't really care. For my usage, the PCC app is kind of 'meh' anyhow. When the subscription runs out in July, I'll delete it.