Offset of Screen

[polarkernel]

I am currently trying to create a board of a Chinese shield, similar to a Lilygo T-Display, in order to male it usable for esp32-smartdisplay. The board is based on an ST7789 driver. Using EEZ-Studio, I was able to run a simple LVGL setup with a label centered on the screen:

However, on the device, this screen is offset like this:

I am not a hardware expert. Does anyone know what could be causing such an offset?

UPDATE:
I was able to correct this issue using DISPLAY_GAP:

      "'-D DISPLAY_WIDTH=135'",
      "'-D DISPLAY_HEIGHT=240'",
      ...
      "'-D DISPLAY_GAP_X=40'",
      "'-D DISPLAY_GAP_Y=52'"

However, I still wonder, how such strange gaps can arise.