The drawbridge between the Lumber Yard and The Mill was raised to prevent the zombies from reaching The Mill.
Lower the bridge near the mill so you can reach Dr. Ned.
Lowered Bridge: 0/1
"Jakobs has hired you to take care of Dr. Ned once and for all. You can find him hidden deep in the Jakobs lumber mill, but the zombie-impeding bridge near the mill needs to be lowered first."
Head to the drawbridge in the Lumber Yard. Use the device the Jakobs Claptrap gave you.
Once again numerous zombies have to be fought off while the bridge lowers. They swarm from all sides. Once all of them are defeated, click on the gate of the drawbridge to turn in the mission and get the next part.
"Now that the bridge is down you can proceed to the mill to find Dr. Ned."
Here We Go Again - It is a good idea to do these two missions simultaneously. Two of the recorders are before the drawbridge and two after it.
The Mission "A Bridge Too Ned" is a reference to the movie "A Bridge Too Far"