Our mobile devices in our data centres are kept in landscape position, and we rotate the device screen programmatically to show the screen orientation on BrowserStack.
However, applications that use the accelerometer or device sensor to detect the actual orientation of the device, change the orientation of the app to landscape mode.
To overcome this, please enable the Honour Device Orientation feature under Android Settings on the vertical toolbar. This should force the app to remain in the portrait mode by default.
