I'm sorry for the problems you had with managing your network objects through the CLI. I guess veyon-cli didn't identify the location(s) properly in which to import the computers. It would be interesting to see the output of
veyon-cli config get BuiltinDirectory/NetworkObjects
before and after the import. May be you can reduce the import to a minimal case with just one entry?
Next I would also recommend to clear all objects before the import.