The first model of the RPi4 seems to have an issue with USB-C, as reported by ArsTechnica in July 2019. The effect is that E-marked cables do not work well.
The Raspberry Foundation has confirmed this issue and wanted to provide a fixed variant in "next few months". That was in July 2019 and a few months are over, so I wonder whether I could distinguish "old" RPi 4 models from "new" RPi4 models.
How do I distinguish RPi4 boards with USB-C issue from the same model with USB-C issue fixed?