ADC Spectra for 6 different channels, all from ~150k events in run 20144010 on 5/24/19, where WPP8TT18 was seen to be "cold" in the shift QA plots, see here.

(left) W PP 1/2 TT 18: these tiles have not had this issue recently, or ever as far as I know. These are for reference.

(middle) W PP 7/8 TT 22: PP8TT22 (black) is the problem channel from the other day (night of 5/22/19, morning of 5/23/19), but in this run did not appear cold in the QA plots. We can still see that it has a large noise peak compared to "good" channels.

(right)  W PP 7/8 TT 18: PP8TT18 (black) was the cold tile in this run. We can see the large noise peak, shifted to the right as compared to PP7, and that there has been a shift in the MIP peak position to higher ADC.

Run 20146025 QA plots, WPP9 TT12, WPP8 TT18+22 exhibit "Cold" behavior: