Hi,
HS_SLEW, HS_RXEQ, HS_TXEQ cannot be adjusted in device tree. For programming the settings, please try to add a service in startup to set the values. You can refer to
Jetson Nano FAQ
Q: How to autorun an app or commands at startup?
It is still possible there is unknown defect in hardware design. We would expect default settings working fine if the custom board is good.