Why ma front camera not working

hi;

The initial problem is: the front camera is not working properly (sometimes working sometimes not), I'm trying to install another app, but the front camera isn't working; I'm reinstalling the phone (factory reset) no new ones.

In addition, when I switch the camera (from the back to the front) there is no possibility to return to the rear camera and camera.app locked, And display the error message: You cannot use more than one app which uses the camera at the same time.The camera will close. If I want to use the rear camera, is obliged to remove data information about: android setup/system, camera, light sensor and cameralyzer.

thanks