I was send too "MikroTik support #[SUP-98849]:" RB411 6.48.6.2) If reboots persist, then generate supout file on router (and latest RouterOS version installed) and send it to support@mikrotik.com
You have right not signal but problem is nstreme in os v5.9.also why you use nstreme? try nv2, it's better.