I have the same problem. I initially noticed when I had both fans set to Balanced, and #1 would spin around 750 RPM and #2 around 1150RPM.
I then set them both to Fixed 1500rpm. #1 spun up to ~1100, and #2 stuck around ~1150. I waited 15-30 seconds after I applied the change to see if it would increase to 1500, but no dice. I did the same thing for 1900rpm, and both fans stayed at the same speeds.
After waiting a minute or 2 longer, it looks like the 2 fans now match RPMs (give or take a few, which is expected).
Next, I moved them both down to Quiet and after a few minutes #1 has dropped down to ~500rpm or below, but #2 is still at ~1150rpm (where it's stayed the whole time I've been changing settings back and forth).
Running iCUE 3.10.125 and Firmware is 1.0.4, this unit was purchased last night.
(If I should put this in my own thread, please let me know).
