Slow refresh rate when controlling a ssd1331 96x64 OLED display with Xiao nrf52840 BLE

Hi, I’ve been trying to control a ssd1331 96x64 OLED display with the Xiao nrf52840 BLE and I noticed that the refresh rate is extremely slow. When I try filling the screen with a solid color, it takes over a second on this small display. When I write pixels to the screen, ie write current time to it, it is very easy to tell that the pixels are being updated from left to right column.

I have the SCL pin on the OLED display connected to the SPI SCK pin on the Xiao board. So I’m wondering if there’s a hidden delay somewhere that I’m not aware of, or if the SPI interface just happens to be too slow.

Any suggestions on how to make the refresh faster?