After some experimentation with time constants, I turned the lock-in amplifier's noise way down. I also reduced the pauses since the system reaches equilibrium much faster. Finally, 100 data points didn't seem to give a much better result than 10, so for the time being I have reduced the number of datapoints taken at each step to 10.

Added baudrate for lockin_controller and changed it to 19200 (must match srs setting).