How can I avoid input coupling by current drawing lines?

Especially in Constant Resistance mode you have to note that an input coupling from the input lines to the voltage measurement may occur if sense lines are used.
Since in constant resistance mode the exact acquisition of the input voltage is important to make the correct current setting a magnetic coupling into the sense lines causing a positive feedback makes the system instable.
At first, you have to reduce the coupling.
That means:
Separate the sense lines from the input lines. Also separate the sense lines from all other lines drawing current, e.g. mains supply.
The sense lines should be twisted to eliminate the induced voltage.
Never twist the sense lines with any of the current drawing lines!
The load input lines should be twisted or at least run in parallel to compensate the magnetic fields.
And of course:
Keep all lines as short as possible!
If all these steps don’t bring the desired success, a capacitor may be connected between the sense lines.