The grid is magnetic. Node centers and edge bends will snap to grid points unless you press and hold CTRL while moving nodes/creating bends.
Are you using the latest version of yEd (3.12.2 at the time of this writing)? There used to be some problems with grid in much older versions.
Dear anonymous poster, welcome to the yEd user forum. We have already asserted that the original poster was referring to resizing nodes while I was referring to moving nodes and bends in the very first comment to my answer.