With AC-68R and firmware 378.56.2, it looks like some USB applications stop working after period of inactivity. I saw it yesterday with media server, when DLNA source was not visible in the LAN; today it was Samba, when the share was not visible in the LAN. In both cases I disabled /reenabled respective server, and they both instantly showed up for everybody. On the other hand, Transmission is working all the time. So I wonder if there's some "inactivity period".