Viktor “Leleka” Lakhno, a former prisoner of war who took part in the air breakthrough to Mariupol, has alleged that one of the servicemen exchanged on 17 July collaborated with the Russians while in captivity. The 35th Separate Marine Brigade, Defence Intelligence of Ukraine (DIU) and the Coordination Headquarters for the Treatment of Prisoners of War have said that they are investigating the claim.
It’s hard to differentiate between willful collaboration and giving infos due to threat of torture. Not an easy case imho.