I built three identical circuits within the same chunk.

I did not attempt to test all possible orientations. For the attached images, east is on the top

What I expected to happen was...:

Input signal from observer fed via repeater into two droppers facing each other. Droppers are initialized with a single item in dropper on the right. All repeaters are set at the default 1-tick.

After removing red block, the item should be in the dropper on the left which powers the lamp.

What actually happened was...:

Only the circuit on the right works.

I do observe a signal from all the observers but it only triggered the dropper in the right circuit.

Steps to Reproduce:
See the attached images for the circuit