Type-C allows for Dual Role Port (DRP), which allows ports to act as both a source and sink. When Try.SNK is enabled, this allows a port that is normally a source to attempt to act as a sink if the other end of the device has no preference. You can prevent this by disabling the try.SNK feature in in register 0x29.
I would also encourage you to make sure that the CCSrcSnk in CCCtrl1 Register (0x027) is set to 0, so the device will never enter Sink Mode (DFP) detection. By changing this register and the bits in the CCCtrl3 Register (0x29), you will eliminate any chance of your device acting as a sink.