Strange spell problems

[Flare]

I'm making a spell based on Maledict in DotA (curses enemy heroes within the spell AoE, dealing slight damage per second. Every 4 seconds of the curse, a hero will take X damage for every 100 damage they have taken over the duration of the curse). For some reason, my spell only works correctly on the first cast. On the first cast, it lasts 12 seconds (as it should) but on every other cast, it lasts roughly 1 second per unit in the spell AoE and sometimes units are immediately killed from about 500hp) even though they SHOULD be removed from the unit group once the spell duration expires. Here's the code

Spoiler

Maledict Cast
    Events
        Unit - A unit Starts the effect of an ability
    Conditions
        (Ability being cast) Equal to Maledict 
    Actions
        Set TargetPt = (Target point of ability being cast)
        Set TargetGroup = (Units within 200.00 of TargetPt matching ((((Matching unit) is A Hero) Equal to True) and ((((Matching unit) is alive) Equal to True) and (((Matching unit) belongs to an enemy of (Owner of (Triggering unit))) Equal to True))))
        Unit Group - Pick every unit in TargetGroup and do (Actions)
            Loop - Actions
                If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                    If - Conditions
                        CustomVal Less than 1000
                    Then - Actions
                        Set CustomVal = (CustomVal + 1)
                    Else - Actions
                        Set CustomVal = 1
                Set Caster[CustomVal] = (Triggering unit)
                Set RandomPt = (Random point in (Playable map area))
                Unit - Create 1 Hidden Dummy for (Owner of (Triggering unit)) at RandomPt facing Default building facing degrees
                Unit - Set the custom value of (Last created unit) to CustomVal
                Set Dummy[CustomVal] = (Last created unit)
                Unit Group - Add Dummy[CustomVal] to DummyGroup
                Set Target[CustomVal] = (Picked unit)
                Unit Group - Add Target[CustomVal] to DamageGroup
                Special Effect - Create a special effect attached to the origin of (Picked unit) using Abilities\Spells\Orc\SpiritLink\SpiritLinkTarget.mdl
                Set MaxDuration[CustomVal] = 12.00
                Set SFX[CustomVal] = (Last created special effect)
                Set DPS[CustomVal] = (5.00 x (Real((Level of Maledict  for Caster[CustomVal]))))
                Set PeriodicDamage[CustomVal] = (10.00 x (Real((Level of Maledict  for Caster[CustomVal]))))
                Trigger - Add to Maledict Damage detection <gen> the event (Unit - Target[CustomVal] Takes damage)
                Custom script:   call RemoveLocation (udg_RandomPt)
        Custom script:   call DestroyGroup (udg_TargetGroup)



Maledict Damage detection
    Events
    Conditions
    Actions
        Unit Group - Pick every unit in DummyGroup and do (Actions)
            Loop - Actions
                Set RandomPt = (Random point in (Playable map area))
                Unit - Create 1 Hidden Dummy for (Owner of (Picked unit)) at RandomPt facing Default building facing degrees
                Unit - Set the custom value of (Last created unit) to (Custom value of (Picked unit))
                Unit - Add a 0.01 second Generic expiration timer to (Last created unit)
                Unit Group - Pick every unit in DamageGroup and do (Actions)
                    Loop - Actions
                        If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                            If - Conditions
                                (Picked unit) Equal to (Triggering unit)
                            Then - Actions
                                Set DamageTaken[(Custom value of (Last created unit))] = (DamageTaken[(Custom value of (Last created unit))] + (Damage taken))
                            Else - Actions



Maledict Effect
    Events
        Time - Every 1.00 seconds of game time
    Conditions
    Actions
        Unit Group - Pick every unit in DummyGroup and do (Actions)
            Loop - Actions
                Set RandomPt = (Random point in (Playable map area))
                Unit - Create 1 Hidden Dummy for (Owner of (Picked unit)) at RandomPt facing Default building facing degrees
                Unit - Set the custom value of (Last created unit) to (Custom value of (Picked unit))
                Unit - Add a 0.01 second Generic expiration timer to (Last created unit)
                Unit Group - Pick every unit in DamageGroup and do (Actions)
                    Loop - Actions
                        If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                            If - Conditions
                                CurrentDuration[(Custom value of (Last created unit))] Less than or equal to MaxDuration[(Custom value of (Last created unit))]
                            Then - Actions
                                If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                                    If - Conditions
                                        (Target[(Custom value of (Last created unit))] is alive) Equal to True
                                    Then - Actions
                                        Set CurrentDuration[(Custom value of (Last created unit))] = (CurrentDuration[(Custom value of (Last created unit))] + 1.00)
                                        Unit - Cause (Last created unit) to damage (Picked unit), dealing PeriodicDamage[(Custom value of (Last created unit))] damage of attack type Spells and damage type Normal
                                        If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                                            If - Conditions
                                                Or - Any (Conditions) are true
                                                    Conditions
                                                        CurrentDuration[(Custom value of (Last created unit))] Equal to 4.00
                                                        CurrentDuration[(Custom value of (Last created unit))] Equal to 8.00
                                                        CurrentDuration[(Custom value of (Last created unit))] Equal to 12.00
                                            Then - Actions
                                                Set Multiplier[(Custom value of (Last created unit))] = ((Integer(DamageTaken[(Custom value of (Last created unit))])) / 100)
                                                Set MultiplierDamage[(Custom value of (Last created unit))] = (PeriodicDamage[(Custom value of (Last created unit))] x (Real(Multiplier[(Custom value of (Last created unit))])))
                                                Unit - Cause (Last created unit) to damage (Picked unit), dealing MultiplierDamage[(Custom value of (Last created unit))] damage of attack type Spells and damage type Normal
                                                If (All Conditions are True) then do (Then Actions) else do (Else Actions)
                                                    If - Conditions
                                                        MultiplierDamage[(Custom value of (Last created unit))] Greater than 0.00
                                                    Then - Actions
                                                    Else - Actions
                                            Else - Actions
                                    Else - Actions
                                        Set CurrentDuration[(Custom value of (Last created unit))] = 0.00
                                        Set DamageTaken[(Custom value of (Last created unit))] = 0.00
                                        Special Effect - Destroy SFX[(Custom value of (Last created unit))]
                                        Unit Group - Remove Dummy[(Custom value of (Last created unit))] from DummyGroup
                                        Unit - Remove Dummy[(Custom value of (Last created unit))] from the game
                                        Unit Group - Remove Target[(Custom value of (Last created unit))] from TargetGroup
                            Else - Actions
                                Set CurrentDuration[(Custom value of (Last created unit))] = 0.00
                                Set DamageTaken[(Custom value of (Last created unit))] = 0.00
                                Special Effect - Destroy SFX[(Custom value of (Last created unit))]
                                Unit Group - Remove Dummy[(Custom value of (Last created unit))] from DummyGroup
                                Unit - Remove Dummy[(Custom value of (Last created unit))] from the game
                                Unit Group - Remove Target[(Custom value of (Last created unit))] from TargetGroup

Also, the damage seems to be fairly random. Sometimes the floating text appears above one unit, but damages a different one