Connection minimserver - UPnP control point unstable - issue NAS/Minimserver?

[mjolink]

I have done some testing but it seems like I can't reach the router via telnet (turned on Telnet in Windows)


1) I read on internet that some routers can't be reached by telnet?! I searched for an option in my router to turn telnet on, but could not find it.
2) My girlfriend has an extra router between her ISP router and e.g. her TV. Would it help if I place that router between the NAS and my Technicolor TG789bvn router?

Currently even restarting / rescanning or stop / start of the minimserver doesn't help anymore to make connection from my control point (it used to help in making connection). I couldn't reach my music via the control point yesterday.