Weird behaviour, unit losing bless mid-battle

[Curious Yellow]

I tried to search for anything about this phenomenon without luck.

I attacked an enemy province with a (1D1E1S) spectral mage raider. His equipment was firebrand, vine shield, skullcap, shroud and winged boots. My bless is E9N4A4, which gave him reinvigoration and regen, and his script was ironskin, personal luck, holdx3, attack. Not sure all this is relevant, but including it in case there are some weird interactions I might not know about.

At the start of the battle everything appeared fine, but as soon as he cast ironskin, the bless disappeared. It's as if ironskin overwrote the bless. I've never seen a blessed unit get unblessed before, is this a known bug? He still won the battle against the PD, but with significantly more risk than necessary.