SPX5 Smartpilot Erratic Control

[wchoffman]

I have installed an SPX5 Smartpilot onto my Catalina 34 using a P70 Control. The unit begins to swing the boat wildly once the Auto feature is engaged. The compass is aligned within 10 degrees, but once Auto is selected, the autopilot holds steady for a few seconds then begins to swing the boat around, bringing us to a Gibe without immediate intervention. This unit has never worked and I am looking for help. The initial controller was returned and ultimately repaired due to hardware fault. Upon return, I could never get it to control the boat. Any ideas on how to solve this issue??