OK looked up the claw info on SK:
Little is known about this item, other than that the claw itself was taken from the corpse of the great beast Kazgaroth. It has multiple enchantments that all become activated when the claw is worn as a ring. The image of the wearer become blurred and more difficult to hit with weapons or target with spells. It has one drawback however, as it seems to fuel its power with the blood of its wearer. Because of this, the wearer of the claw will often be more sickly and therefore more susceptible to poisons.
STATISTICS:
Armor Class: +1 bonus
Missile Armor Class bonus: +4 bonus
Save vs Death: -4 penalty
Save vs Wands: +3 bonus
Save vs Polymorph: +3 bonus
Save vs Breath: +3 bonus
Save vs Spells: +3 bonus
Constitution modifier: -2 penalty
it must be a bug then. As my theory seems to be wrong.
I wouldnt worry about it, afterall it is helping not hindering
