Has anyone used the Sparki LCD with U8glib?

I wants to use the U8glib library to replace the default LCD library to save RAM. However, for some wired reason, the graphics are not displayed properly. Everything works fine for roughly 0.2s in the beginning, but after that the entire background suddenly turned white. I can still kind of see the graphic, but it is very hard to see the graphics in a all-white background.
Has anyone encountered this situation before?
By the way, I saw a ZK_CS and a ZK_SO pin in the schematic, but I couldn’t find it elsewhere. What does these 2 pins do? Is the problem caused by these 2 pins??

Thanks a lot.

I used the default GraphicTest program in U8glib, and for device constructor I tried U8GLIB_DOGM128,U8GLIB_LM6059 and U8GLIB_LM6063.

Sounds like the contrast isn’t being set properly.