Sounds like a hardware issue. Do a full wipe and restore to stock ucmc1 and try again. If switching to front camera freezes and crashes out of the camera app then it is hardware.
Buy a front camera off eBay, watch a YouTube video if you haven't opened one of these phones so you don't break anything, and finally swap it out!
Cheers,
C64
Sent from my SAMSUNG-SGH-I727 using xda app-developers app
Thank you. I did a full wipe and re-install the stock ROM, but I still did not work. I bought from ebay front camera, when it comes to going to change.