opaque forum
Often encounters like "Ancient Battlefield" or "Grave of Rot." have inherent failure chances for de-buffs to be applied or resisted against. Even with heroes with excessive resistance and accuracy failures occur when applying, removing or resisting de-buffs and buffs.
The encounters often have strict requirements that rely on the above being successful. This leads to repeated attempts in order to get past the hidden RNG code.
Please be more transparent about this during the encounter or better yet fix and remove it entirely.