doesn't find/search for networks after a certain time of running

[sevku]

My Computer stops searching for networks after a certain time of running. Only a restart helps. Turning on and off the wireless network does not help.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: network-manager-gnome 0.9.10.1-0ubuntu7
ProcVersionSignature: Ubuntu 4.2.0-16.19-generic 4.2.3
Uname: Linux 4.2.0-16-generic x86_64
ApportVersion: 2.19.1-0ubuntu4
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Nov 3 18:13:12 2015
ExecutablePath: /usr/bin/nm-connection-editor
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2015-08-13 (82 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
IpRoute:
 default via 10.210.208.1 dev wlan0 proto static metric 600
 10.210.208.0/22 dev wlan0 proto kernel scope link src 10.210.209.126 metric 600
 169.254.0.0/16 dev wlan0 scope link metric 1000
 185.12.129.33 via 10.210.208.1 dev wlan0 proto dhcp metric 600
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
ProcEnviron:
 LANGUAGE=de_DE
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: network-manager-applet
UpgradeStatus: Upgraded to wily on 2015-10-27 (6 days ago)
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH CONNECTION CON-UUID CON-PATH
 wlan0 wifi connected /org/freedesktop/NetworkManager/Devices/0 SBB-FREE c900b6c6-1b75-46ed-84e9-af7c22b07390 /org/freedesktop/NetworkManager/ActiveConnection/0
 eth0 ethernet unavailable /org/freedesktop/NetworkManager/Devices/1 -- -- --
 lo loopback unmanaged /org/freedesktop/NetworkManager/Devices/2 -- -- --
nmcli-nm: Error: command ['nmcli', '-f', 'all', 'nm'] failed with exit code 2: Error: Object 'nm' is unknown, try 'nmcli help'.