Default [Q] LG L5 E610 issue (proximity sensor or calling by itself)

I have an LG L5 E610 which has a strange issue, sometimes the proximity sensor won't turn itself off (in the case of incoming call, in outgoing calls seems to do just fine). Also, during the call, the phone itself calls some other contact from the contacts list, which in turn leads to the dropping of call. I think this issue has something to do with the issue with proximity sensor. Tried factory reset, no good. It's on stock ROM, not rooted.

Is this a common issue, has anyone else had these issues before and how to solve it?