Good day Jan-Willem,
Sorry to get back to you so late, it took a while before i got feedback form R&D on your question 🙁
According to there findings, when connecting the USB Keyboard ( in your case) and Ehternet Cable first, and than latest the power cable to USB TYpe C, it should work.
When connecting the power cable first, it could lead to issues like you have encountered.
Sorry for the inconvenience.

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