OK, lets try to get to the bottom of this, I'm a man of science and I find it puzzling that we can't all find out what's going on here and I find it telling and frustrating that Samsung is MIA on this.
Here are some facts:
- More than a few of us here on the forums (and other forums) have this issue, with a variety of carriers, on both the S7 and S7 edge, and it's safe to assume we all use different apps and software etc. How many in the grand scheme of things? No way to know for sure, but it's a problem for more than a few.
- Some have solved the issue via settings
- Some have solved the issue with changing cards
- Some have solved the issue with a phone exchange
- Some have solved the issue via factory reset
Is each one solved? Maybe, maybe not. Time will tell.
What's the commonality? (not the carrier or apps or cards)
- The phone hardware (i.e. SD card tray)
- The OS (Marshmallow)
Now we need some hypotheses and a way to test them. The hypotheses are easy to come up with, the experimental evidence not so much, but here's some theories (I'd love to hear some more):
- Bad batch of phone with faulty contacts: maybe different card manufacturers have contacts on the cards that are microns thicker or thinner which, when combined with the contacts in the phone, will lead to these varied results. This is supported by the fact that people reusing the cards from earlier model phones are now having issues. Also perhaps supported in that those who fixed it by changing cards actually re-seated the card in such a way to make better contact.
- Marshmallow issue: All the solutions that have been found are placebos or temporary and a software fix is in the works to solve this and end it once and for all
As for myself, the latest thing I tried was to turn off the System UI battery optimization and I haven't had the notification in over 5 hours. I'm not hopeful as I've been fooled into thinking I've fixed it before (factory reset). Or I merely suppressed the notification itself, while the issue causing it is still occurring.
Anyway, looking forward to more evidence and anecdotes and I hate to say it, but there's some solace in knowing 'm not alone with this issue.