Quick answer: The player takes a step or stumbles after impact; they can't hold the finish with the weight on the lead foot and the trail foot up on its toes.
What it does to the ball
Wide dispersion and random contact: the shot inherits the body's loss of control.
Root causes (by frequency)
Swinging beyond the effort level they can control
A downswing sequence out of order
An unstable base at address (weight in the heels or toes)
How to fix it
The 3-second finish rule: hold a balanced finish until the ball lands; if you can't, drop to 80% effort
Drills that fix it
Statue finish · 10 min · 20 reps
Calibrate the maximum effort you can control Hit each ball and hold the finish for a full 3 seconds: weight over the lead foot, trail foot up on its toes and belt buckle at the target. If you wobble, the next ball goes at 80% effort. Find your top speed with a statue finish.
Feet together · 10 min · 15 reps
Rediscover balance and tempo from the ground up Hit balls with an 8-iron and your feet together. Only a balanced swing makes good contact: any excess throws you off instantly. Once you string 8 good strikes, open to your normal stance and keep the feeling.
Frequently asked questions
What is "Loss of balance at the finish" in the golf swing?
The player takes a step or stumbles after impact; they can't hold the finish with the weight on the lead foot and the trail foot up on its toes.
What does loss of balance at the finish do to the ball?
Wide dispersion and random contact: the shot inherits the body's loss of control.
How do you fix loss of balance at the finish?
The 3-second finish rule: hold a balanced finish until the ball lands; if you can't, drop to 80% effort
Sources
Harvey Penick — Harvey Penick's Little Red Book
Dr. Young-Hoo Kwon, Texas Woman's University — Golf Biomechanics Instructor Program (secuencia cinemática, plano funcional)