Pixhawk 4 Mini Telem 1 Companion Computer: high packet loss


I have a Pixhawk 4 Mini and have been using a Raspberry Pi Zero companion computer on Telem 1. I recently noticed that the physical connection between my Pixhawk and the Pi Zero was dropping 70-90% of my packets. About ~70% when I set a 115200 BAUD and ~90% with 921600 BAUD. Might there be a problem with the grounding? Has anyone else experienced high packet loss?

Also, I noticed that in APM they have RTS/CTS control that they recommend disabling. I’m not doing flow control over my UART connection. Is there something in the Pixhawk parameters that I would need to change?