How is this a sat nav blunder, did the sat nav know he was driving a truck, are the sat nav instructions compulsory, hasn't the driver passed a driving test where he had been taught to be aware of his vehicles size, read road signs, read the road, and look where you are going?

Its 100% a driver blunder.

A bit like calling getting caught for speeding 'an accelerator blunder'. The biggest problem in a lot of vehicles is the nut behind the wheel.

PBSC

Problem between seat and controls