I have the exact same issue, my phone will be working completely fine and then all of a sudden my phone goes into emergency contact mode with no signal. I wait for a few minutes to see if it comes back and nothing..... As soon as I restart my phone everything works perfectly again, it seems that I have to restart my phone two - three times a day now!
I have had my note 5 for just under 2 months now, using a corporate plan from Rogers. Not entirely sure what to do with this problem.
My Note5 does the same thing from time to time. I'm assuming it's because of the SIM card is a bit loose inside the slot. I can't prove that, so I won't even bother going to the dealership to get my phone checked. I'm worried they'll replace it with a refurbished one after I paid full price for the phone...
GOOD POINT. I am agree with u that the sim card slot is a little bit bigger. But it does not explain the reboot phone, everything is back to normal.
Phone will need to be rebooted when you install a SIM card. My guess is that when the card was loose and then re-positioned itself in its proper place, you'll need to restart the phone to enable the phone to read the SIM card again.