Two Platinum Electrodes having Potential Difference

I use Potentiodynamic polarisation scan using Saturated Calomel as Reference and Platinum electrode as Counter electrode. Platinum
Electrode is a 1cm by 1cm flag type. A few months ago, I started getting unusual results, and while trying to locate problem, I found that my two platinum electrode give a potential difference against other (open circuit, just the two platinum electrode in electrolyte). This potential difference is not stable, varies continuously between -300mV to +300mV. What is wrong here? I have checked they are not leaking. Do I need Platinum Electrode cleaning, and how can I clean them? They do not have any visible products on them.
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