A comment on the local controls large output: the voltage range at the output of the DAC is +/- 10 Volts. So If the correction signal is out of this range (as in the case of picture 1) the output is saturating and the control loop is likely not to be working properly (as can be seen from the large RMS in picture1).

More in general, looking at the error singnal, it seems to me that we are still affected by the "spikes issue". It could be useful to compare the open loop rms with the reference values in the absence of spikes.