This is a companion example to the design: "TDFS Impedance Stability of Transmission Line Fed LED Driver - Switching". In this version, a switch is added to turn on two of the LEDs after 2 ms, to inject a load transient into the system. This transient will expose the severity of the damped ringing response at the converter input, or system instability if the source/load impedance ratio is inadequate.
The initial configuration for this design uses a cable length of 400 meters with 8 AWG = 2.1 mOhm/meter conductors, and a converter input capacitor = 22uF. This is consistent with the companion design. You can try using an increased cable length (e.g. 800 meters, 5 AWG = 1 mOhm/meter) by making a copy of this design and re-running the simulation. You will see that the circuit becomes unstable at that longer length. You can also try larger values of input capacitance, to mitigate the instability problem.