I have the same problem with the S6 Active, it's not consistent, it happens about 30% of the time. I would say it's a driver issue.
Too many issues with this phone.
One more thing, a few months ago I was in the Middle East with my Galaxy S2. I had rooted it then unrooted it so the unlock code needed to be reapplied (the unlock code is always the same for a specific phone, once you have it it won't change). I confused my unlocked code with the protection...
It's a lot easier than that. I had my old Blackberry as well as the Galaxy S2 unlocked by AT&T itself. As a matter of fact I just got out of the chat with AT&T tech dept (go under Contact on the AT&T website then choose chat) regarding getting an unlock code for my Galaxy S4 Active which I got...