So while I was doing all this, I created one EIGRP based lab and tried to introduce lots of possible issue. But of course, I ended up into an issue which originally wasn't part of the thought process. So let me quickly bring it up with relatively smaller topology:
Alright... Was just kidding :-) ... Below is the topology you need:
Here is the relevant configuration to begin with:
so can you troubleshoot ? Good Luck....