I've spent over 20 hours trying to calibrate my Epson PJ using an old Colormunki Display.
I have been struggling to get passed White Balance.
I was often getting erratic readings, and being a beginner, I thought that was normal.
I now realise (with a bit of research) that the erratic readings are due to the Colormunki being connected to a USB 3.0 port instead of a USB 2.0 port (which I don't have).
I eventually found a suggestion from X-Rite who said that several users have solved the problem by using a powered USB 2.0 hub.
BTW, I didn't find this information on their website, I found by an independant google search.
I have ordered a Belkin 4 port powered USB2.0 hub.
I'll let everyone know if this solves my problem, But I thought I would post this here in case others are having the same problem.
EDIT : I have also found other comments where users believe that the problem wasn't so much the USB 3.0, but the fact that many colorimeters need 6 volts, whereas most USB ports in laptops, etc. only provide 5 volts.