Thanks for the u8g2 logo picture. I think the display is brocken: The second half of the internal display RAM does not work. Your display should work correctly with U8G2_SSD1306_128X64_NONAME_1_HW_I2C constructor, but it doesn't.
Yet I still have some doubts: Are you sure it is a 128x64 display? It looks more like 96x48 version.
Oliver