Comparator Doesn't update its output

I am creating item counter, consist of two weighted pressure plate and a long line of redstone. When I am try using it, comparator doesn't automatically update itself. I must right-click it to update it. So I test the comparator.

So how to reproduce this bug
1. made and system like 18.59.25
2. Flip lever B
3.Flip Lever C
4.Flip lever B again. Output still send