//
// ENCODER SETTINGS
//
// This option overrides the default number of encoder pulses needed to
// produce one step. Should be increased for high-resolution encoders.
//
//#define ENCODER_PULSES_PER_STEP 4
//
// Use this option to override the number of step signals required to
// move between next/prev menu items.
//
//#define ENCODER_STEPS_PER_MENU_ITEM 1
But it sounds more like a worn out/dodgy encoder