Using 10t/sec clocks will sometimes glitch out testforblock and comparator

I was creating a minigame so when you mine a block you will get points and I am using "/testforblock 0 57 -3 air" and than "/setblock 0 57 -3 stone" it works but sometimes comparator after first command block stays on.

Tested on 10t/sec clock and 20t/sec /fill clock

EDIT: Using /fill instead /setblock works fine.