Here's a snippet of another article that came out today and it mentions how the Serbian government could take NIS private this fall. This would make the sanction issue go away as well.

https://carnegieendowment.org/politika/87959

EU sanctions on Russian energy exports are likely to shrink Russia’s economic presence in the Balkans significantly, disrupting some of the flows of Russian oil and gas that have long been a mainstay of trade relations with the region. Serbia has ostentatiously resisted EU pressure to join the sanctions regime, which has had a negative impact on NIS, the country’s major oil company. Gazprom Neft until recently held the majority stake, which served as a key symbol of Russian political and economic influence in Serbia. However, Croatia plans to implement EU sanctions that will cut off NIS’s ability to import Russian oil starting in December. Due to fears of other secondary sanctions, Vucic has indicated that he may need to nationalize NIS this fall and sell Gazprom Neft’s remaining stake in the company to another buyer to keep it operational.