Yes, the QA/QC technician calibrates them every morning, and I tested the waters using three different pH electrodes with all similar results. However, titratable acidity was also performed on the distilled water and it was virtually zero (meaning the smallest drop of 0.1 N NaOH raises pH to over 10 and titration stops).
Also, distilled water having a low pH is not uncommon. If you look on internet, you will see many websites asking about this (mostly people with aquariums asking if it is ok for fish with lower pH). Most give the reason Curiouscat does being dissolved CO2 (as carbonic acid). I just found it very strange the boron was 14 times higher in the distilled water than the tap water, yet the same tap water supplies that distiller unit.