Fire Field not decaying TFS 1.0

[Tort]

When creating fire fields throught this spell the created fire fields never decay.

local delay = 5000

local combatfire = createCombatObject()

arr = {
{0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0},
{0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0},
{0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0},
{0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0},
{0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0},
{1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1},
{0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0},
{0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0},
{0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0},
{0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0},
{0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0},
}

local area = createCombatArea(arr)
setCombatArea(combatfire, area)

local function spellCallback(param)
    if isCreature(param.cid) then   
        a = math.random(0,9)
        if a == 1 and isCreature(param.cid) then
            addEvent(doSendMagicEffect,delay,param.pos, CONST_ME_FIREATTACK)
            addEvent(doCreateItem,delay,1487,1,param.pos)
        elseif a == 2 and isCreature(param.cid) then
            addEvent(doSendMagicEffect,delay,param.pos, CONST_ME_FIREATTACK)
            addEvent(doCreateItem,delay,1488,1,param.pos)
        elseif a == 3 or a == 4 and isCreature(param.cid) then
            addEvent(doSendMagicEffect,delay,param.pos, CONST_ME_FIREATTACK)
            addEvent(doCreateItem,delay,1489,1,param.pos)
        end
    end
end

function onTargetTile(cid, pos)
    local param = {}
    param.cid = cid
    param.pos = pos
    param.count = 0
    spellCallback(param)
end

setCombatCallback(combatfire, CALLBACK_PARAM_TARGETTILE, "onTargetTile")

function onCastSpell(cid, var)
    return doCombat(cid, combatfire, var)
end

But according to the items.xml they should properly decay after 120sec

    <item id="1487" article="a" name="fire field">
        <attribute key="type" value="magicfield" />
        <attribute key="decayTo" value="1488" />
        <attribute key="duration" value="120" />
        <attribute key="field" value="fire">
            <attribute key="damage" value="20" />
            <attribute key="ticks" value="10000" />
            <attribute key="count" value="7" />
            <attribute key="damage" value="10" />
        </attribute>
    </item>
    <item id="1488" article="a" name="fire field">
        <attribute key="type" value="magicfield" />
        <attribute key="decayTo" value="1489" />
        <attribute key="duration" value="120" />
        <attribute key="field" value="fire">
            <attribute key="ticks" value="10000" />
            <attribute key="count" value="7" />
            <attribute key="damage" value="10" />
        </attribute>
    </item>
    <item id="1489" article="a" name="fire field">
        <attribute key="type" value="magicfield" />
        <attribute key="decayTo" value="0" />
        <attribute key="duration" value="120" />
        <attribute key="field" value="fire" />
    </item>

Does anyone have an idea why they don't decay? When using fire field runes or creating the fire fields myself they do decay. I'm using TFS 1.0