Has anyone else noticed inconsistency with this core?

Sometimes it just stops working. And no, I'm not always getting cursed more than once a minute resulting getting cursed. I've seen it a few times now where I've not has a curse cast at me for over a minute, and the very first curse that targets me lands. I remove it, then over a minute later (with no curse attempts in between) another curse lands.

As an example, last night I was in a LVoD, and several of us has Ward Against Darkness. When Suul would do his raid wide curse, half of us were immune and would not get cursed, and the other half always got cursed. For the entire raid the ones who didn't get cursed remained immune to curse the whole time (it was only normal, and it appears he only does his curse on normal slower than 1/minute, so Ward Against Darkness should render you safe on normal), while those who also have Ward Against Darkness but were getting cursed got cursed every single time. We checked combat logs and at no point were additional curses being attempted on those who were getting cursed every time despite having supposed immunity.