This is not something I usually see. In fact, it is usually the opposite.
Over-active right bicep muscle, not Releasing the Fourth Power Accumulator sufficiently, Off-Plane, fear of hurting the right elbow are places to begin...Is the player even capable of physicaly straightening it ?
Per 7-1, For the Swinger, CF Uncocks both the Left Wrist and Right Elbow; 7-19 and 7-20. So both must remain Passive, but never Whippy.
First place I'd look is plane. If you can't straighten the right arm down and OUT, you are probably over plane through impact.
Split grip drills, no ball, just in the air, below horizontal, but not lowered all the way to a full swing.
Focus on first - not letting the clubhead get 'inside' the hands until hip high, and second, swinging OUT - from about 7 to 2 on a clock as your right arm straightens to 2 o'clock.
If that doesn't help you get a good feel for how the right arm needs the 'room' to straighten, next look to your pivot. You may not be turning through very well.
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