You don't show what Y is, or what your screen orientation is set to. If I remember correctly, if any part of a sprite gets pushed offscreen, the sprite will be truncated. So make sure the bounds of the sprite are within the 320 x 240 pixels of the LCD when you push it. The paramaters to pushSprite are the "upper left corner" of where you want the sprite to be placed.
Look through the examples at https://github.com/m5stack/M5Stack/tree/master/examples/Advanced/Display/Sprite to failiarize yourself.