Connecting data lines of this e-paper display to 5V IO pins is also a bad idea; it will shorten its lifetime.
Did you connect the data lines directly to your AVR Arduino with its 5V IO pins?
If you did, this will feed the 5V voltage through protection diodes to the display, and disturb SPI communication.
Use level converters with 5V Arduino, or at least series resistors (e.g. 4.7k) on data lines.