No control over stamp brush. Automatically switched to a graphic brush. At times I also have difficulty in getting the circle area to appear. Just the cross hairs. Thanks!

The clone stamp brush can be any brush you like. With the clone stamp tool selected, you can select the brush shape in the brush panel or in the options bar.
To reset it to the default, then with the clone stamp selected then click the down arrow next to the stamp in the options bar. Then click on the small ‘cog’ and click ‘Reset tool’.
 

Dave

Until one of the wizards comes out from behind their curtain with a better answer, you could try --

• resetting the Clone tool
• failing that, resetting Settings