I had the same problem with cm-12.1-20160608-UNOFFICIAL-nevisp and after reading through the forums, I discovered that others did too.
I'm also using cm-12.1-20160118-UNOFFICIAL-nevisp, but I can't seem to use WhatsApp without the phone crashing every few hours.
CM11 had trouble playing videos in WhatsApp, so I moved to CM12. I still have not found a stable build that can do just Youtube, Whatsapp, and basic calls without crashing or poor performance. Have you tried the CM13 release by faizauthar12?
Originally Posted by eximiusnl
I discovered that above problem is only with the most recent release of the 8th of June '16. I was able to flash the second last release of the 18th of januari '16 without a problem. Pretty strange. Did anybody had the same problem as me?