You do not extend the network if you are using ethernet between them..
Do not tick the extend network on the TC.. Do not use extend a network on the AEBS.
Do as follows.
1. Set the AEBS to bridge.
2. Set the wireless in the AEBS to create a network.
3. Set the wireless name and security.. here you have two choices.. but most likely you want roaming. So set them exactly the same as the TC.
4. Lock channels on both TC and the AEBS to different values. This is not 100% required but I think will help stability. The auto setting should be able to keep them from interferring.
If you actually want to use extend the network.. disconnect the ethernet.. you are repeating over wireless.