Lycia Unholy Heretic Periodically Unkillable During First Phase

I've been running a high-damage glass cannon for quite a few Sanctums, but have run into Lycia two times killing me in the first phase (with the Gargoyles). She does this by dashing, then immediately entering her "You cannot escape Beidat's Gaze!" channeled attack. During this attack, she appears to be unkillable (400m+/2.5s damage Penance Brand of Dissipation is unable to end her attack early, at least).
At the end of her channel she swipes, and while I'm pretty sure it is actually dodgeable, I'm usually too caught off guard by her still hitting me over and over to respond properly and die.
After her final swipe, she retreats to the second stage, with the "Playing with fire will get you burned..." dialogue playing. I am unsure if she lost the last bit of health to trigger this before or after her channel ended, as my brands were likely still active (my memory isn't perfect, and I wasn't recording).
While I'm unsure if this is a 'bug', it feels unintended as it seems virtually guaranteed to end any no-hit run if it occurs - Presumably, you're meant to kill her before she can enter that phase, but her being able to do so within a second of activating seems potentially impossible. This has only happened twice in a few tens of runs, but it's disconcerting to say the least.