Anointed Peacekeeper.
When playing the Anointed Peacekeeper card on mtg arena today, I noticed the 2 mana increase cost did not apply to the card I chose of my opponent. He played it at the regular cost. My Anointed Peacekeeper was on the board at the time still.

-
DThrash94#13712 commented
Today, 1/25/25 my OP had peacekeeper naming Into The Floodmaw and I was able to cast it for a single Blue mana as normal. Bugged still
-
Krautty Jr#75571 commented
Just had this happen to me as well.
05/13/2024 -
SnapcasterMage#88438 commented
If you`re wondering, it hasn`t been fixed yet. Got the same issue right now, 20/08/2023
-
ScholarX#42847 commented
The same thing happened to me today, 10/11/22, at approx. 11:55am Eastern US. In a match with an opponent, I used Anointed Peacekeeper to drive up the cost of their Make Disappear. While I got to see the opponent's hand and choose with the Peacekeeper as usual, the cost of the chosen card did not appear to change. On a later turn when the opponent only had 3 blue mana available (meaning I should have been safe against Make Disappear which should now cost 4 mana total), the opponent used Make Disappear to counter one of my spells for just 2 mana (no creature was sacrificed for its Casualty in this case). This should not have been able to occur, please fix this bug a.s.a.p. Thank you.
-
Ender245#26034 commented
This just happened to me as well