I have what I believe to be a solution to our problem. That is, I saw someone else's solution and wanted to spread it as much as possible. In this post over in the other 99.5% problem thread, CB123 details it for us:
@CB123 said: I have found a workaround!
What you need is copy the following two directories from a working machine, or a copy from a friend.
/Users/"your user name"/Library/Application Support/Telltale Games/TheWalkingDead/SyncFs/Data/WalkingDead103
/Users/"Your user name"/Library/Application Support/Telltale Games/TheWalkingDead/SyncFs/Meta
Copy these two directories onto your own machine with the EP3 problem. Make sure you don't overwrite any other folders.
EP3 then works. I've had three other people test it successfully.
This is where we can help each other out. I have been able to download episode 3, but every time I try to download episode 2 it stops at 99.5%. If there is anyone out there who has episode 2 but not episode 3, I will gladly trade you the folders. All we have to do is to go to the folders, compress them into zip files, and email them to each other. Then we can unzip the folders, put them in their proper place, and if CB123 is right, then we should be able to play.
If you like this idea, reply back here or send me a PM and we can work out the details. We can all help each other out and FINALLY be able to fix what Telltale hasn't.