Having same or similar issue.
When swapping from Back facing camera to front, the camera image initializes upside down and is frozen. Swapping back to Rear facing camera has same results.
Exiting the scene and returning restores the camera behavior until a swap is requested again.
No errors in device logs or xCode debugger
Not happening with previous version of vuforia v4.0.105
Devices: iPad2 or later / iPhone 4 or later