DRL problem

Hello,

I am a Biomedical student from Portugal and I was developing a eeg board
(only the analog part) based on the schematics of the Modular EEG. I have
however one problem with the DRL, as I can't make it to work properly.
Indeed I have better results if I connect directly the 3rd electrode to the
GND.
Before someone asks I did however some modifications and I would want to
know if this could be the problem for the DRL or not.
Ok so from the INA114 I use a buffer just like Modular EEG, however I am
using the LF412 then on the inverting amplifier I also connected a 10M
resistor parallel to c216 (1nF) for stability (I think) and again used a
LF412.

I would appreciate any input.

Thanks,

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