enchanted items can lag the game hard.
how to recreate :
step 1 :
enchant boots (mine were enchanted with : Soul speed 3, frost walker 2, Protection 4, unbreaking 3, mending 1)
step 2 :
fill a shulker box with these boots.
step 3 :
fill a chest with these shulkers.
step 4 : CRTL + middle click (Copy) the chest and put it in an itemframe, this should make the game lag.