I try to remember as much as possible. First off, I'm aware of deathwish and that there is a leader and there are even cards (both units and ability) that can activate such deathwish. But here it was a deck that concentrated on just one thing: Adding bleeding to my cards. All names I use are from GwentUP, so I hope they are correct. At one point 2/3 of my full field were bleeding. Cards used were
Dettlaff
Plumard
Cutthroat
Orianna
Queen of the night
Garkain
and some others that I don't exactly recall, but inflict bleeding.
None of the (I don't know the right word) growing cards were involved and only two cards with deathwish, that I could control quickly. It might have been coincidence, but the strange behaviour started right after two Oriannas were on the battlefield. That deck was exactly the same from two different players, and I faced it 4 times with repeating results, which is that non-bleeding units disappeared most probably (I'm really not sure exactly, because there was a lot of action per round from the bleeding and it was difficult to see any coherences) when one of my units died from bleeding. It must be a game mechanic, since the non-bleeding, no-animation disappearing ones were counted to the graveyard.