This, I believe, is caused by a special set of circumstances. The spell Shrink is called from this modifier
<GameModifier>
<ModType>Unit</ModType>
<Attribute>MeleeAppliesSpell</Attribute>
<StrVal>Shrink</StrVal>
<Provides>Victims are shrunk, halving their Attack and giving them +50% to Dodge</Provides>
</GameModifier>
The Shrink spelldef has this
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Attack_Boost</StrVal>
<DisplayName>Shrunk</DisplayName>
<Duration>-1</Duration>
<Calculate InternalName="Calc" ValueOwner="TargetUnit">
<Expression><![CDATA[[UnitStat_CombinedAttack] * -0.5]]></Expression>
</Calculate>
<Calculate InternalName="Calc2" ValueOwner="TargetUnit">
<Expression><![CDATA[[Unit_GetTroopCount]]]></Expression>
</Calculate>
<Calculate InternalName="Value">
<Expression><![CDATA[[Calc] / [Calc2]]]></Expression>
</Calculate>
</GameModifier>
but that is not working and I think it is because when you
1) Call any spell from meleeappliesspell and
2) Use a calculate tag where ValueOwner="TargetUnit"
3) The value it returns is always 0 (divide by 0 returns the huge negative number)
in words, when you call a spell from MeleeAppliesSpell and it has a Calculate tag with ValueOwner="TargetUnit" this always fails to retrieve the value.
This used to work. I had several modded items and traits that I tested before 0.915 that used this method and they worked, but they no longer work now.
I really hope you will consider fixing the underlying issue instead of just changing the mace. It is a very useful tool when it comes to making interesting modded items and traits.