A lot of CX, from the data I have; they have not good factory calibration.
C9 had better factory calibration.
You can see that by looking at the RGB Separation using Profile of Primary before starting calibration. (with contrast @ 85 and Color @ 50)
You can improve the factory problem by taking multiple Profile of Primary Color and compare RGB separation charts using different Contrast settings (84, 83, 82, 81, 80) and then Color (51, 52, 53, 54, 55).
Most of the time, the factory problem's improvement will come by setting Contrast @ 80 and Color at 54-55, but each unit may need different values.
When you have issues with the input signal, you can use the HDMI Diagnosis menu to determine what signal TV is receiving: https://www.avsforum.com/threads/2019-lg-oled-calibration-and-user-settings-no-price-talk.3042154/post-58775690
You can use the HDMI Override menu to force HDR10 to an SDR signaling of DeckLink cards (they use Hd Fury for that with C9, with CX that secret menu can be used):https://liftgammagain.com/forum/index.php?threads/lg-oled-terrible-uniformity.14741/#post-147306
If you have dimming issues with 2018/2019/2020 models, you can disable GSR:https://www.avsforum.com/threads/lg-oleds-3d-lut-profiling-using-lightspace-thread.3043520/post-60048600
If you have a problem with any older DeckLink card with HD output, then you can disable the Deep Color to the specific HDMI you have connected the DeckLink card:https://www.avsforum.com/threads/lg-oleds-3d-lut-profiling-using-lightspace-thread.3043520/post-58376942
Your HDMI port will become 300 MHz, work like HDMI 1.4, without HDR support.
If you have problems to pre-calibrate 109% White using SM Menu, you can ignore it and let the 3D LUT fix it.
You have to determine which OLED Light setting will provide you 124 nits @ 109% White.
Use regular TV menu RGB High controls to pre-calibrate 109% (keep one channel at the default position, reduce the other two channels only).
When you have 124 nits @ 109% White, let's say by using R High 0, G High -6, B High -15, then restore these controls to 0.0.0 and start the 3D LUT profiling.
This trick will determine which OLED light will provide you 124 nits in post-calibration.
You will do this as we don't want the problematic regular TV menu to have active processing, so ColourSpace and the 3D LUT will fix these issues.