Network shares problem

I'm having problem with my network neighborhood.

If I have just rebooted my router then I can see my Asus router-NAS. However, after sometime, usually overnight, the Asus router-NAS is no longer there. I can see the other devices attached to the network but not the Asus router-NAS.

My Asus router-NAS is named without any spaces so I think its not the problem. Also, I can see it in my network if I'd reboot the router. I can also access my Asus router-NAS using ftp. Transmission detects it as well. I can also see it as media share. But not as a NAS.