Welcome to the forum.
It may be useful to disassemble the mechanism for inspection, followed by service and potential part replacement.
That drive disc is retained by a center axle bolt, w/ a flat screwdriver slot on the tip, plus a nut.
On mine, the rotation of the disc on the axle shaft was not smooth. I got acceptable feel by packing the internal (inaccessible) bearing w/ wheel bearing grease.
Other possible issues are a worn driven disc, w/ the perimeter rubber worn away, worn / weak springs, crud in the belt pulley, worn belts, worn idler pulleys or a worn actuator spring.
The easy way to work the problem is to start the machine and see what is spinning or not, then repeat when the drive lever is activated. If that process is used, then it might need to be repeated because of several problems.