ToME: the Tales of Maj'Eyal

So for context, I'm playing a TW, and was in the Maze. The Horror grappled me, and I attempted to use Thread Walk (with dual weapons equipped). As a result, the spell fizzled and an attack was made against the Horror (all in one action, as if the attack from Thread Walk was still occuring). This did not trigger cooldown on Thread Walk, nor did the turn counter progress - none of my buffs / debuffs changed duration after this. Nothing attacked me after making this attack. I did this (i.e. attempted to use Thread Walk) 4-5 times in a row and killed the boss without the boss acting again, without the cooldown ever triggering, and the spell fizzling each time.

Hopefully that is clear..

I think i've had that happen sometimes, mostly while being pinned/stunned, but I haven't been able to reproduce it