Yes that blog confirms my suspicions, they are crap.
Remember your motor is only rated to take that current at 5V, and it is an inductive load which can play havoc with even well designed switch mode regulators.
It is not just a matter of copying the circuit in the data sheet it needs a proper PCB layout, and quality control of components used. Also I suspect the small size of the module is also contributing to the problems. These chips are normally used on a much larger board with a larger ground plane.
I have managed specialist power supply engineers in my time and I know what a struggle getting it right is. Bin and move on.