Block updating is very laggy

I built a redstone circuit (an extremely simple one) and it works then all of a sudden it stops then works again. The blocks around me sometimes dont update so I cant tell if a door is open or if I put some redstone on the ground. I also watched a video on youtube where a guy had put mob heads on a wall and the wall didnt update and so it looked like nothing was on the wall and then it finally updated.
https://www.youtube.com/watch?v=w40t06J9Ydg check this video out at like 3:51 and you will see what I am talking about