Mine turns very easily by hand. As the A10 pump is a 'rotating gear' type, there really should be no stiffness - unless it is full of very cold SAE50 oil of course!

You should certainly take it apart and investigate. You can't afford to take any chances with an oil pump. As a guess the bottom plate might have a 'pick-up' on it and addressing this on an oil stone might solve your problem.
Adrian