Dropper -Item -Comparator Bug

A line of droppers all facing into the same way
beeing powered with pulses through the redstone wire above it.
There is a comparator facing out of each dropper.
the first dropper is filled with blocks, so that it should act as a counter triggered by powering the line of redstone above it.
But for some reasons it seams to jump over some droppers which are not putting out a comparator signal, and are not containing any item,
as shown in the picture.