Errors when building for dedicated server

So I’ve been following this guide:

To create a dedicated server for a multiplayer fps.

Now I’ve followed the tutorial twice (clean both times) and have come to the same point twice now.

I end up successfully cooking the content, then build the server and client, then when I run the server I get this log in the server (including a messagebox that shows all the default property warnings and errors):

The client gives a similar messagebox of property warnings and errors and also shows a messagebox afterwards which says:

Assertion failed: GDefaultMaterials[Domain] != NULL [File:D:\Projects2\Unreal Projects\EngineBuild\Engine\Source\Runtime\Engine\Private\Materials\Material.cpp] [Line: 351]
Cannot load default material

What can I do and more importantly, what have I done wrong?

For now I have fixed it by ignoring the tutorial in step 8 (“Deploy: Do not deploy”) and actually choosing to deploy to my device, this set the files in the right locations.