Now Event Server binding to the wrong ethernet adapter

I have an issue where a Now Event server keeps binding to the wrong ethernet adapter. It is supposed to be bound to en0 but keeps slipping back to en1. Everytime I change it, hit apply, then relaunch it has switched back to en1. I have tried deactivating en1 while restarting the server and it complains that en1 isn't there and then reluctantly uses en0 until en1 becomes active again.

Anyone seen this issue before?