You are hitting the 2 main issues I'm working with DJI to fix...
1) The DJI SDK reports camera OFF, when it's really ON during GS flight. The app uses the SDK reported state to control buttons so, since the SDK says the camera is OFF during GS, pressing the button will always try to turn it ON, no matter what. For GS missions I suggest allowing the auto-camera mode to work; it doesn't use status and turns the camera ON when motors start and OFF at the end when motors are turned OFF.
2) For some reason the Galaxy models seam to have more issues with the SDK. Before the last release they would shut down when starting apps (even the Vision app for a while) and while DJI fixed many of the issues the random lock-ups and app shut-downs resist (albeit less often). Some Samsung models are more prone to the issue, other less (I use a Samsung Tab S and it's 90% OK). While I continue to work with DJI on fixes I have found that waiting to connect the device to Wi-Fi until after the Phantom completes initialization often helps (either that or it just feels like it helps, I'm not sure).
I am hopeful that either I am able to find a good way to stop the issues by moving code around within the app and changing the SDK timing or that DJI issues an update that fixes them but for now all I can do it the former and hope the later comes soon.
Thanks,
Ken