Unpaid visa fine in Russia, do I take a risk going to airport transit area in Moscow?

In August 2015 I crossed the Russian-Mongolian border with an expired visa without realizing it. The border police noticed it and made me pay ( along with a colleague in the same case) a fine of about 50€. It was quite complicated because nobody spoke English. Before we crossed the border, we were given another paper, in Cyrillic, with an amount to pay to a bank account. We never paid this amount.

I'll fly in August 2020 to Japan with a flight that transits to Moscow (less than 2 hours of connection so no visa required). What can happen to me during my transit through the international zone (my arrival and departure flights are in the same terminal)? Will I be checked with my passport and if so can I be seen that I have an unpaid fine or an inadmissibility? Can I be denied access to the international zone, or access to the flight to Japan? Is there a risk of arrest?

I have a European passport