Homemaker 5kg washing machine blocked drain

Have a Homemaker brand top load washing machine. Stopped working during a wash and gave an error code that means the outlet drain line was blocked. The water that was still in the machine drained easily when the drain hose was layed on the ground but i am wondering how to check for this 'blocked drain'. Has no centre piece on the inside of the bowl, just holes in the bottom for bubbles. There is a single screw in the centre of the bowls which is very tight & did not want to unscrew to check under the base of the bowl & i didnt want to force it & break something. I opened the back and disconnected the drain line & it appeared there was nothing blocking the small final pump from a visual inspection. Any suggestion would be appreciated, thanks.