automatic hopper route dedector cannot dedect route true

What I expected to happen was...:
in hopper line one of the hoppers gives items to the right and one of the hoppers takes items from that hopper , think must happen is belowe hopper must take items only if right hopper cant give items but...

What actually happened was...:
hoppers normaly give 1 item in 1 tick and line of hoppers works slow , becouse of that there is a automatic hopper route dedector which takes items from 1st hopper to the last hopper immediately, but in some situations this goes wrong and think must happen in above pharagraph do not happen