Hi there! This error is actually expected at the moment.
The reason is that we are using a shortcut mechanism at the moment called “Default Routing”. It offers all the Join packets to all of the “Default Routers” (aka: OUI addresses or endpoints) that Helium operates.
The final design we are converging on soon will look-up whether that (AppEui,DevEui) is the routing table of each OUI. The OUI maintains a copy of this table on the blockchain which all the miners can reference at any time.
I am currently working on some documentation that will go into more depth on this soon (including details on how to purchase and operate an OUI) so keep an eye out on our devdocs site.