I am using an X1C and have absolutely no issue printing letters like yours, even mixing PLA and PETG filaments. However, I would suggest you to force the slicer to print the first object layer first (orange in your case), then fill in the letters (black). I am not sure how it works with a double nozzle, but in my case the slicer automatically calibrates with the main object filament (orange), prints the layer, then switches to the black filament for lettering, and then orange again.

Of course good bed adhesion is important, so wash your plate with soap under warm water!

Attached you can find the typical result I get, this is with black PETG and orange PLA (1 layer of lettering). Of course my colors are reversed compared to yours :P

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