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Saturday 11 November 2017 at 17:19
is the ball clipping the bottom of the diverter (as you say) while the diverter is in motion, or when it's in it's rested 'up' position? if it's when it's rested, you'll have to adjust the set screw at the bottom of the mechanism to prevent that from happening.
Source: http://pinside.com/pinball/forum/topic/dialed-in-le-left-ramp-shot-results-in-lost-ball#post-4068847