Quick answer: The stroke's tempo changes from putt to putt: some strokes long and lazy, others short and jabby; long putts finish at random distances from the hole.
What it does to the ball
Without a constant rhythm no distance chart is possible: lag putting becomes a lottery and the three-putts show up.
Root causes (by frequency)
Regulating distance by hitting harder or softer instead of with the length of the backswing
No repeatable inner beat that survives pressure
How to fix it
Same rhythm always, different length: count 'one-two' on every putt — a longer or shorter backswing sets the distance, the beat never changes
Drills that fix it
The one-two beat · 15 min · 18 reps
Set a constant rhythm and regulate distance with backswing length only Pick three distances (3, 6 and 9 paces) and putt to each one counting quietly 'one' on the backswing and 'two' at impact, always at the same beat. The only thing that changes between distances is the length of the backswing, never the speed of the count. Three balls to each distance; if the beat speeds up on the long ones, restart the round.
The ladder · 15 min · 16 reps
Calibrate speed on long putts Place 4 tees at 3, 6, 9 and 12 paces. Putt to each distance going up the ladder and back down, trying to die each ball at its tee. Count how many finish within one pace and beat your record every session.
Frequently asked questions
What is "Variable stroke rhythm (uncalibrated lag)" in the golf swing?
The stroke's tempo changes from putt to putt: some strokes long and lazy, others short and jabby; long putts finish at random distances from the hole.
What does variable stroke rhythm (uncalibrated lag) do to the ball?
Without a constant rhythm no distance chart is possible: lag putting becomes a lottery and the three-putts show up.
How do you fix variable stroke rhythm (uncalibrated lag)?
Same rhythm always, different length: count 'one-two' on every putt — a longer or shorter backswing sets the distance, the beat never changes
Sources
Dave Stockton (con Matthew Rudy) — Unconscious Putting