Comment 3 for bug 1415702

There's enough information on this bug report to actually do something useful:

Jan 28 19:33:14 clevo NetworkManager[27189]: <warn> (hfp/2CD05A55C693_0C3E9FAE619C): failed to look up interface index
Jan 28 19:33:14 clevo NetworkManager[27189]: <info> (hfp/2CD05A55C693_0C3E9FAE619C): device state change: unmanaged -> unavailable (reason 'none') [10 20 0]
Jan 28 19:33:14 clevo NetworkManager[27189]: <error> [1422495194.170276] [NetworkManagerUtils.c:1252] ASSERT_VALID_PATH_COMPONENT(): Failed asserting path component: NULL
Jan 28 19:33:14 clevo NetworkManager[27189]: FATAL: Failed asserting path component: hfp/2CD05A55C693_0C3E9FAE619C
Jan 28 19:33:14 clevo kernel: [ 432.098680] do_trap: 1 callbacks suppressed
Jan 28 19:33:14 clevo kernel: [ 432.098688] traps: NetworkManager[27189] trap int3 ip:7f42584edf90 sp:7fff1dcb1610 error:0

I'll keep the bug open as a master bug for this occurance; but please still try to file the bug report from the crash dump if you can in case there is more to it.

Workaround is to remove any phone device paired in bluetooth if it's not needed. Alternatively, stopping the ofono service should also let NetworkManager run properly.