ToME: the Tales of Maj'Eyal

The Corrosive Slashes sustain from the Wretchling demon seed goes on cooldown every time I kill an enemy with Corpathus. I think this may be because Corpathus changes on kill, leading the game to believe I equipped/unequipped the weapon and its demon seed. The sustain, accordingly, goes on cooldown even though I have not actually changed weapons.

"to believe I equipped/unequipped the weapon"
does it go on cooldown when you swap to offhand? an offhand with a valid weapon set.