ECMP routing shows @unknown at Gateways

I am facing a problem on which i can’t find any posts at the forum.
I am doing a ecmp routing with 3 ppoe interfaces and 2 interfaces behind adsl routers which can’t become modem’s or they are not leting ppoe passthrou.
I got this strange “@unknown” entry after i manually add static routes.
The ecmp route works though.
Any ideas ?
winbox_2017-04-13_11-56-54.png

Hi.

This happens when router didn’t find the interface you have already add. Maybe if you disconnect your USB modem the interface could disappear in interface list.