Maybe a "Dispel Magic" is being cast at the location.
or
It maybe your trigger.
EDIT: I'm almost done w/ ur spell xD
Heres the spell! Sorry, I forgot to pass it to you yesterday. xD Good luck
The "Menssageiro" unit is most probably a structure am i correct? then better remove the "remove blight" ability from that unit in the unit editor and the blight wont be removed after construction has been finished.