Hi @chris!
Wow, I’m so sorry to see that the USB controller discovery feature is causing so many troubles 
At first I thought that the feature will really help new users (and I hope that it is helping), but it’s being a pain in the ass for already working networks.
@Mark_Webster the appearance of a new device in the inbox should not affect the already working Z-Wave devices, this cannot be the root of the problem.
The problem that we are facing here is the following one: as the Z-Wave USB controller doesn’t provide a unique identifier to the OS, the binding “sees” a new device even if the Thing is already configured. In any case, the solution should be pretty easy and shouldn’t cause any trouble: just ignore it.
Anyway, for the new upcoming openHAB 2.4 release, we should recommend deleting all Z-Wave things: the nodes and the controller. It should only take 5 minutes to import all things again and link the already created items. It’s not the best solution, but it should solve all problems forever.
Best regards,
Aitor