Knight of the Reliquary ETB effect only triggers once. [Investigating]

Avacyn

Hello,

Her ETB only triggers from the first copy. when the text stats "When this creature enters the battlefield it gets +2/+2 for each land in your graveyard." 

Everything else about her works correctly. when a support of any kind is destroy she well fetch the next land and gives it 6 mana. it just her ETB effect stops working after the first cast. if you were to cast another copy of her it well just give 4/4 without counting the number of land in your graveyard. 

//Edited Title -Brigby