Hello!
I had an issue that on N2 of the game, I attempted to target [@2] as Seer, who had claimed Spy, but I was unable too. I targeted [@2] initially, but then swapped it for a different person the night before. I am sure that I had chosen different people than [@2], and that I had never used my ability on them. They were also not a revealed role, but they were simply untargetable with Seer.