I'm wondering what is causing a segfault within NetworkManager - I see this in dmesg:
NetworkManager: segfault at 8 ip 0000000000479ef7 sp 00007ffc2607cc10 error 4 in NetworkManager[400000+23b000]
A segmentation fault is typically due to a programming error or at least a special case that was not considered appropriately by the developers (e.g. memory allocation that failed, buffer overflow, etc.).
Unless you are one of those, as a mere user there is probably nothing you can do about it except reporting the problem to them. If NetworkManager was provided by your distribution, then it's preferable to report the bug to the package maintainers (i.e. through https://launchpad.net/ for Ubuntu, https://www.debian.org/Bugs/ for Debian, etc.)