E-Ink Shield clearScreen artifacts


I bought an E-Ink Display Shield v1.0 03/01/2013.
Started the first example “displayCharacter” from SeeedEink.zip library May 2013 version. When clearing the display before writing there are some artifacts like shown in the attached picture.
This leads to a background after writing characters that appears grey instead of white - still showing the random pixel relics.
On youtube I found a video showing the correct clear procedure youtube. com/watch?v=Otoha8Aql2A where the screen is completely black before writing of character starts.
I already searched the Seeedstudio forum, but it seems that nobody else posted about a similar issue.
Tested the shield with an Arduino Uno and Mega 2560, with no difference using Arduino 1.6.7 IDE.

Did anyone else have this issue? Is there an error in the Eink library?

Thanks in advance,