This article is from the Model Trains FAQ, by Christopher D Coleman with numerous contributions by others.
This is a generic defect and most corral sets suffer from it. It is
caused by the fact that the car vibrator does not work as well as the
corral vibrator. Sometimes adjusting the spring on the car vibrator
plunger will help, but no reliable solution has been found. If yours
works count your blessings.
 
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