The graph is confusing, ET and BT are in opposite directions, that can't happen in actual physics...

But I can't blame the device alone from the start... never happened to me... could be an USB power spike as well.

Yes that is what I thought - very strange, at the moment - I'm not sure whether it's the Mastech, PC or cable causing the problem. I'm contemplating ditching the Mastech in favour of Phidgets - though there's no guarantee there either...