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Build Identifier: 

I've been experiencing this issue for several weeks (I can only guess it
occurred since the update to NetworkManager 1.8.0): 
https://bugs.archlinux.org/task/54076
>From what I can see Factory is also on 1.8.0 and not yet 1.8.1+ which contains
the fix.
(installed versions: 
NetworkManager-pptp-1.2.4-1.3.x86_64
NetworkManager-openvpn-1.2.10-1.1.x86_64
NetworkManager-connection-editor-1.8.2-1.1.x86_64
NetworkManager-applet-1.8.2-1.1.x86_64
typelib-1_0-NetworkManager-1_0-1.8.0-1.1.x86_64
NetworkManager-1.8.0-1.1.x86_64
NetworkManager-vpnc-1.2.4-2.2.x86_64
NetworkManager-branding-openSUSE-42.1-1.10.noarch
libKF5NetworkManagerQt6-5.35.0-1.1.x86_64
)

journalctl -r excerpt:
ul 07 20:40:26 rabin.tus systemd[1]: NetworkManager.service: Service hold-off
time over, scheduling restart.
Jul 07 20:40:26 rabin.tus systemd-coredump[10898]: Process 8928
(NetworkManager) of user 0 dumped core.
Jul 07 20:40:26 rabin.tus systemd[1]: ^[[0;1;39mNetworkManager.service: Failed
with result 'core-dump'.
Jul 07 20:40:26 rabin.tus systemd[1]: ^[[0;1;39mNetworkManager.service: Unit
entered failed state.
Jul 07 20:40:26 rabin.tus systemd[1]: ^[[0;1;39mNetworkManager.service: Main
process exited, code=dumped, status=11/SEGV
Jul 07 20:40:26 rabin.tus systemd[1]: Started Process Core Dump (PID 10895/UID
0).
Jul 07 20:40:26 rabin.tus NetworkManager[8928]:
^[[0;1;39mg_array_sort_with_data: assertion 'array != NULL' failed
Jul 07 20:40:26 rabin.tus NetworkManager[8928]:
((src/platform/nm-platform.c:2650)): assertion '<dropped>' failed
Jul 07 20:40:26 rabin.tus kernel: NetworkManager[8928]: segfault at 8 ip
00005644ee78ddef sp 00007ffcd0c33830 error 4 in
NetworkManager[5644ee6da000+252000]
Jul 07 20:40:26 rabin.tus NetworkManager[8928]: <info>  [1499456426.5119] dhcp4
(bnep0): dhclient started with pid 10893
Jul 07 20:40:26 rabin.tus NetworkManager[8928]: <info>  [1499456426.5100] dhcp4
(bnep0): activation: beginning transaction (timeout in 45 seconds)
Jul 07 20:40:26 rabin.tus NetworkManager[8928]: <info>  [1499456426.5097]
device (90:3C:92:EF:A3:95): state change: config -> ip-config (reason 'none')
[50 70 0]
Jul 07 20:40:26 rabin.tus systemd-udevd[10890]: ^[[0;1;39mcould not rename
interface '4' from 'bnep0' to 'enp0s20f0u3': Device or resource busy
Jul 07 20:40:26 rabin.tus systemd-udevd[10890]: Error changing net interface
name 'bnep0' to 'enp0s20f0u3': Device or resource busy
Jul 07 20:40:26 rabin.tus systemd-udevd[10890]: link_config: autonegotiation is
unset or enabled, the speed and duplex are not writable.
Jul 07 20:40:26 rabin.tus NetworkManager[8928]: <info>  [1499456426.5055]
device (90:3C:92:EF:A3:95): Activation: (bluetooth) Stage 2 of 5 (Device
Configure) successful. Will connect via PAN.
Jul 07 20:40:26 rabin.tus bluetoothd[1623]: bnep0 connected
Jul 07 20:40:25 rabin.tus NetworkManager[8928]: <info>  [1499456425.3482]
device (90:3C:92:EF:A3:95): state change: prepare -> config (reason 'none') [40
50 0]
Jul 07 20:40:25 rabin.tus NetworkManager[8928]: <info>  [1499456425.3478]
device (90:3C:92:EF:A3:95): state change: disconnected -> prepare (reason
'none') [30 40 0]
Jul 07 20:40:25 rabin.tus NetworkManager[8928]: <info>  [1499456425.3477]
audit: op="connection-activate" uuid="da357faf-af35-4246-918d-a5f5cdaef100"
name="Keysersoze Network" pid=2356 uid=1000 result="success"
Jul 07 20:40:25 rabin.tus NetworkManager[8928]: <info>  [1499456425.3476]
device (90:3C:92:EF:A3:95): Activation: starting connection 'Keysersoze
Network' (da357faf-af35-4246-918d-a5f5cdaef100)
Jul 07 20:40:22 rabin.tus ModemManager[1527]: <info>  (net/bnep0): released by
modem /sys/devices/pci0000:00/0000:00:14.0/usb1/1-3
Jul 07 20:40:22 rabin.tus NetworkManager[8928]: <info>  [1499456422.5351]
device (90:3C:92:EF:A3:95): state change: failed -> disconnected (reason
'none') [120 30 0]
Jul 07 20:40:22 rabin.tus NetworkManager[8928]: ^[[0;1;39m<warn> 
[1499456422.5302] device (90:3C:92:EF:A3:95): Activation: failed for connection
'Keysersoze Network'
Jul 07 20:40:22 rabin.tus NetworkManager[8928]: <info>  [1499456422.5292]
device (90:3C:92:EF:A3:95): state change: config -> failed (reason
'bluetooth-failed') [50 120 44]
Jul 07 20:40:22 rabin.tus NetworkManager[8928]: ^[[0;1;39m<warn> 
[1499456422.5291] device (90:3C:92:EF:A3:95): Error connecting with bluez:
GDBus.Error:org.bluez.Error.Failed: Operation already in progress
Jul 07 20:40:22 rabin.tus NetworkManager[8928]: <info>  [1499456422.5220]
device (90:3C:92:EF:A3:95): state change: prepare -> config (reason 'none') [40
50 0]
Jul 07 20:40:22 rabin.tus NetworkManager[8928]: <info>  [1499456422.5216]
device (90:3C:92:EF:A3:95): state change: disconnected -> prepare (reason
'none') [30 40 0]
Jul 07 20:40:22 rabin.tus NetworkManager[8928]: <info>  [1499456422.5215]
audit: op="connection-activate" uuid="da357faf-af35-4246-918d-a5f5cdaef100"
name="Keysersoze Network" pid=2356 uid=1000 result="success"
Jul 07 20:40:22 rabin.tus NetworkManager[8928]: <info>  [1499456422.5213]
device (90:3C:92:EF:A3:95): Activation: starting connection 'Keysersoze
Network' (da357faf-af35-4246-918d-a5f5cdaef100)

Confirmed with another out of date Tumbleweed install still running NM 1.6.
that the bluetooth network connection via my phone works fine.

I've marked this a major, as for me at least, being able to tether to my phone
is pretty essential (I'm bound too wifi NOOOOO ;) - having said that, I'm sure
I could find a way to connect without NM, but given that it's the recommended
approach, I'd say there'll be a non trivial amount of users affected by this at
some point. Feel free to drop it however.

Reproducible: Always

Steps to Reproduce:
1.Create bluetooth phone connection which can be tethered (and enabled on the
phone)
2. Simply try to connect via the NetworkManager popup from the icon
3. Crash should occur within a second or two
Actual Results:  
NetworkManager crashes and restarts

Expected Results:  
Not crash

PC is a Dell XPS 9360 Laptop, latest Tumbleweed updates (as of today).