When you drop down the menu to click on or off settings every once an a while the portrait one disappears. The phones screen rotates horizontally (which I hate) and I can't change it. It's as if the portrait option sneaks away for a little break. Then it comes back as if no one notices. I took screan shots and sent them to a friend who has 9S as well to see if I was crazy. She couldn't find the portrait then it appeared in new pic.
Hey there! Have you tried clearing the cache partition of the phone?
Turn off the device.
Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
When the Android logo displays, release all three keys.
An ‘Installing system update’ message will show for 30 – 60 seconds before the Android system recovery menu options appear.
Press the Volume down key several times to highlight wipe cache partition.
Press Power key to select.
Press the Volume down key to highlight yes, them and press the Power key to select.
When the wipe cache partition is complete, Reboot system now is highlighted.
Press the Power key to restart the device.