When vinyl cracks, it often creates sharp edges that stand above the surrounding surface.
Even the most skillful repairs often result in a slightly elevated mound. This will be more pronounced using an air-dry filler like ours, lest you shave off the high spots with a razor blade.
A better method is to melt the edges with a heat gun, press them with a grain pad, and then follow with a heat-cure filler. Nevertheless, a near-perfect result is difficult to achieve.
If the original vinyl cracked, a repair cannot be expected to last any longer. It may be just as expensive to reupholster or replace the component.