ACS806 and ACM604V60-01-1000 tuning

Hi, I have the ACS806 (V2) driver and ACM604V60-01-1000 servo motor (well, 4 pairs...), and I'm struggling to get started. The current tuning response dips below the purple line (negative current?), whilst the manual makes it look like it should return to the purple line. Any attempt at motion is violently jerky and trips the over-current. See attached for current trace.

There are certain configuration values (inductance, inertia, resistance, etc.) the software won't let me set - I'm not sure if that's related. I have set rated current, motor pole pairs, encoder lines and position following limit at least.

Further plot, showing what happens if I try the position loop, even with very low values.