execute tp multiple times in a single gametick cause selector by position to fail?

I first find this during map making and I can't figure out what's the problem
so I rewrote the function to a test world
much to my surprise it happen without trying to hide

I wrote this function so that I can give an entity a position

function summary:
if a specific entity exists execute anchor summon a finder
do
if finder is found within the radius of 1 (r=1) of specific entity kill finder
if finder is on the bottom of specific entity then finder x+1
if finder is on the left of specific entity then finder z+1
loop if find finder
kill specific entity <<< I minus the part where I do something with it after finder give it pos

what should happen:
specific entity and finder should be killed and function should end

what actually happen:
after a short region away from anchor,
finder isn't killed yet tp to specific entity thus stuck in a endless loop

demonstration video
https://drive.google.com/open?id=0B10qKZg3-v5FZm1IMXFlZzkzNVk

p.s. I don't know what's the bug so the summary is very likely to be false