Seems a bit high even with LPF, but in the nA range that could just be noise in general.
You would also want to shorten the inputs to see if that still happens, I would expect not under normal circumstances.
How do you mount your OLED, directly to the header as seen in the guide, or using wiring?
I do test all units for low noise and all that, including with OLED readings and without OLED (scope).