Changing the redstone repeater marked on attached picture into redstone wire makes piston in the middle extend 2 times as 1-tick pulse. When using repeater the piston extends only once as 2-tick pulse like it's supposed to.

This is 2-tick detector, so output should give short pulse only at 2-tick pulse. When piston extends twice as 1-tick pulse, torch gives out 3-tick pulse instead of 2-ticks, which the torch detects and unintended behavior happens.

EDIT: Also, when using clock instead of "redstone dust->solid block on sticky piston pointing upwards->repeater" pulse generator, the whole system doesn't work as intended. Although, if clock is 1-tick pulse, and the repeater marked on attachment is set to 2-ticks, this works again.

EDIT 2: This seems to be directional bug, sending power from the left side via wire seems to work.

EDIT 3: http://youtu.be/aB38AwJhYD4