My S6 is experiencing similar issues. Mine has been ongoing since 16Sep. I don't recall when my phone upgraded to 5.1.1 but it's there now. My issues are the auto screen rotation, step counter in S_Health, and auto brightness adjuster no longer work. They will only work immediately after restarting the phone. And, the step counter will only work immediately after the restart AND while the screen is active. Meaning, as soon as I tap the power button to turn off the screen or when it times out, the counter stops working. It won't count again until I restart the phone.
I chatted with Samsung Support the other night and they, of course, blamed it all on 3rd party apps. They had me do a hard reset on my phone. The phone was wiped clean but the features still don't work. Not sure what's going on but I'm a bit aggravated these features aren't working.
Has anyone else experienced these issues with the S6? If so, what resolved the issues?
Thanks!