No video after using camera in other Activity

G'day all,We are using de QCAR library for detecting images and it works well (resolution good be better, but that's another issue)After detecting the program calls the stopCamera() function and switched over to another activity. If the user wants to detect another images the AR activity is resumed and the function startCamera() is called.So far so good. The problem occurs if the other activity is using the camera (front of back) for taking a snapshot of the user. After releasing the camera, stopping the preview and setting the previewCallBack back to null, the QCAR library can't initialize the cameraDevice anymore (QCAR::CameraDevice::getInstance().init() returns false) and the camera image is black (size (0,0))Am I doing something wrong or do I forget somethingAll help is welcome!