I'm using lenovo vibe x2 ........I got the same issue that, " contact manager has stopped unfortunately"...I got irritated lots of times ..when I want to make a call...one day I fedup with the this error dialog box and made factory reset to check for same issues will occure or not in future .....until now i didn't get any problem with contact manager issue ...in my case factory reset worked ....warning : before going to do factory reset back up Ur data........hope this may help...