volatile cores in thread maps can be invisible

map underground sea
t16
rare monsters have volatile cores
the entire map only 2 cores were visible, the others were not on screen and didnt have any activation animation.

I also just had this happen to me in a Defiled Cathedral Memory Strand map with Volatile Cores. I visibly watched the cores explode a good half-screen away from me and I still died to it. No effect for the explosion radius, nothing. Just dead as they disappeared.