Merc's dropping gear with wrong stats after duels

The merc I killed did NOT drop the helm with the same stats that it was wearing before the duel stareted ... when it was equipped on it prior to the duel the helm showed +13 spell sup, 100+ life, 25+ chaos res , AND eldrich implicits.

After defeating it in the duel the help that dropped has NONE of those stats as advertised prior to the duel ....

second time this happened