Shower valve supply pipe Joint leak - Whatwent wrong??

Help please!!

Found a leak in the supply pipe joint (cpvc to copper) feeding into the shower valve, behind the shower panel of bath

Please see video of leak here:
https://drive.google.com/open?id=1Rt...VSaXjCxsGcshRi

Location: California Date Built: 2009-2010

Thanks much!

Via RSSMix.com Mix ID 8247361 http://www.rssmix.com/