Bumping the **** outta this. Same issue on a build one year later (Cm13 Oct 01/2016 Celox). Contacts and phone stopped working. So I replaced them with Google's AOSP variants from the play store. At that point, the phone reboots when I try to call. The 3g works wtf...
Yes, this was sent from my SGH-I727R by I'd rather be making calls with this. Also, incoming calls work. Just outgoing is the issue. Can't be my radio, right? Cm11 or 10 whatever it was worked flawlessly on the same one.
Ok, so after jerking around the apps, disabling/re-enabling the system dialer, etc., I received a call from my friend. At the point, all four soft keys stopped working while the calling issue completely fixed itself. After a reboot, the soft keys and the calling work flawlessly 0.0
Typical Android issues...
Although my friend is complaining about some beeping noise coming from my end during a call. Will look into it.
So current fix (for now): disable/re-enable the inbuilt contacts and dialer apps, reboot, enable them, clear their data, cache, whatever it takes, etc. Keep doing so until it magically fixes itself. Maybe try getting a buddy to call you and pick up. That is all I can think of in order to reproduce such weirdness :/