Zolin Blood Priest healing off downed priestess

The twin bosses at the end of the Vaal interlude normally has Zolin heal off his sister but and maybe I'm wrong and it's not a bug but he persists doing so even if you take her down first...
He didn't do that the first time I fought them but during that fight he siphoned her down, this time I took her down and he is constantly siphoning off of her even tho she has no more HP...

mine also, unable to progress
Bug Report ID: #1874267502

Same me also, fight never ends he just keeps transfusing from her even though she's dead.

Same here. Finally killed him, but it was reading 4.4 mil damage done before it reset. Then did another 400k to him before he finally died. Assumed it was probably a bug, but you never know with these guys.