Update:
Disabling the CMU with the command from Full range RGB strange behavior on Nvidia Jetson AGX Xavier Developer Kit
echo 0 | sudo tee /sys/class/graphics/fb0/device/cmu_enable
eliminated all errors except the gray value with index 0 (black). See this post for comparison with CMU enabled.
Eliminating this single error was achieved by adjusting the default_srgb_regamma_lut[] on empirical basis.
Best regards
Bruno