They just reversed the values in Close and Adjusted Close fields, clueless as to why, probably incompetence.
Only the Close field is adjusted, rest doesn't seem to be adjusted for anything (even the Adjusted Close).
Well, you are right in that they replaced the Close with AdjClose, but the new AdjClose is not the same as the old Close. The quotes seems to be (or could be) adjusted for splits and dividends now, but only for a certain period going back in time.
The Close is not adjusted:
[...]
Date Open High Low Close AdjClose Volume
07/01/77 25,03294 25,14273 24,48397 6,82375 24,92315 143200
06/01/77 25,08784 25,36232 24,86825 6,853809 25,03294 168700
05/01/77 25,25253 25,6368 24,92315 6,868836 25,08784 191000
04/01/77 25,58191 25,6917 25,19763 6,913929 25,25253 143200
03/01/77 25,52701 25,80149 25,52701 7,004109 25,58191 169800
[...]
If nothing else, the quotes look pretty much self-consistent now. For example the Open and Close are almost always within the high/low boundaries for most symbols. But different sources give completely different numbers overall.
For example, this is a recent sample of XRX from Quandl, allegedly adjusted:
XRX,09/06/2017,27.66,28.1,27.54,27.7,1332878
XRX,12/06/2017,27.7,28.54,27.7,28.18,1608300
XRX,13/06/2017,28.22,28.38,27.94,27.98,958192
XRX,14/06/2017,27.98,28.08,27.38,27.66,1520918
XRX,15/06/2017,27.37,28.08,27.12,27.73,3439830
XRX,16/06/2017,27.82,28.78,27.78,28.44,7196084
XRX,19/06/2017,28.66,28.93,28.48,28.73,3161082
XRX,20/06/2017,28.67,28.82,28.25,28.27,2442766
XRX,21/06/2017,28.23,28.27,27.71,27.82,2152005
XRX,22/06/2017,27.89,27.97,27.7,27.91,2208391
XRX,23/06/2017,27.94,28.42,27.85,28.38,4035911
XRX,26/06/2017,28.46,29.24,28.46,29.13,5372156
XRX,27/06/2017,29.13,29.34,28.88,28.92,3972327
XRX,28/06/2017,29.01,29.46,28.96,29.29,3300774
XRX,29/06/2017,29.32,29.36,28.88,29.12,3783566
XRX,30/06/2017,29.27,29.34,28.72,28.73,2818863
XRX,03/07/2017,28.78,29.23,28.68,28.85,1511483
XRX,05/07/2017,28.9,29,28.34,28.45,2939727
XRX,06/07/2017,28.24,28.46,28.05,28.35,3067750
XRX,07/07/2017,28.41,28.91,28.41,28.78,3142489
XRX,10/07/2017,28.8,28.97,28.7,28.88,2339977
They are already quite different from Yahoo even in recent days. So which one is right? I suspect that if you were to compare 10 different sources you would get as many different results.