(0.12.6) Bug: Devices sometimes just aren't being constructed.
Workers do other things and seemingly ignore it.
Did you had components in two storages?
In a situation when device requires for example 10 components and you have like 5 in one storage and 5 in another transport job was not able to arrange itself (problem existed for stack less than 100 kg).
I'm adding handling of that exact situation in next update, I've stumbled upon it while building DockPort :D