I got that too ...thought it had to with a theme I applied and did not bother to report (besides had some xposed mods so was not sure what it was-too lazy to go to base installation to try the clock) Thanks!
In my case it reboots but then freezes up again like when I go to the clock app to say clear the data (which I cannot do as the touch function freezes and the reboot starts again) I went to twrp and cleared just the data for the clock there (no need of full wipe)...but then dared not touch the clock again..it worked
not sure about wifi but cellular data-wise it is slower to latch on to the network compared to Omni (esp if going from bad network area to a better signal area - i have had to toggle airplane mode or sometimes simply reboot to get it to hook up to the network) omni is like stock-very quick 4g recognition
I am now using a Alarm Clock found in F-Droid.org
Also trying to Encrypt Phone but it is still in the Marshmallow animation for about 35 minutes, still waiting... for it to complete if not then I am not going to use full data encryption...