When Da Undatakah uses his battlecry to gain Test Subject’s deathrattle, he is no longer returning spells cast on him to my hand when he dies. I’ve tested this with Seance, Power Word: Shield, and Vivid Nightmare in both solo games and in Play mode. The Undatakah + Seance with the Test Subject deathrattle was working just a few days ago when I built the deck, but at some point it seems to have broken.
Edit: Just played another two games and it seems to be working again.
What other deathrattles did he have? The ones that he gains are picked in a random order, and if one that returns him to the hand or deck triggers before the others, it can negate the other deathrattles.
The bug is happening again. The only deathrattles he has are from test subjects, and after casting seance on him he gains the Storing Spell buff. But when he dies the seance isn’t returned to my hand.
I’ve been playing a weird deck and it is definitely not working for me. My only test experience was when the undatakah only gained 3 test subject deathrattles.