You don;t know the troubles you have to go though with high Z stuff. Phenolic at 10-11 ohm-cm is pretty crappy. See **broken link removed**.
Hey I could measure the conductivity of a piece of paper at work. A film of Acetone on glass is conductive.
It's probably the board material. You might be better off with FR-4 and Teflon/PTFE standoffs when required. Guarding is also important.
The flux will be conductive too if not removed. So will, believe it or not, fingerprints.