good judgement in the care of reef animals is harder to develop than the technical knowledge of reefkeeping. i wouldnt have assumed that the high pH reading was wrong, if the pH probe passed initial standardized pH calibration. pH, temp, salinity critical parameters that can crash a tank quickly. pH reading of 12 have been seen with kalk overdose, of 6 with CO2 overdose (carx).
1. new ph probe calibration
2. abnormal pH reading- check tank with another pH test (colorimetric test, or another separate handheld pH probe test)
3. normal reading with another test method, your tank still appears normal (big sigh of relief)- test new pH probe in another stable tank that got a normal reading with the 2nd test method (cross check)
4. conclusion- new ph probe is not calibrated/ not working- repair or replace the new probe
sorry so dogmatic, i preach crash prevention