@mwe Perhaps you're trying to ping the wifi interface from another machine? Because the ssv6051 suffered a problem with the broadcast ARP packets that has been solved in the mainline flavour of the kernel, which does not work with NAND yet.
In practice the driver does not respond to ARP packets, so the wifi interface does not "announce" itself to others when asked to. The presence of the ethernet may cause some side effects that let the interface announce deliberately and so it works.
