Google Nexus 5 :: Can't Answer Incoming Calls On 4.4.2

I have a Nexus 5 running Android Kit Kat 4.4.2. Overall this is a great phone but i am facing some issues that i will describe below:

1) This i noticed 2 months ago. I dont know if it still has it: I was calling a friend and he didnt answer. Then the whole day i was waiting for him to call back but he never did (at least according to my phone). When i called him again he told me that he called me back, the phone rang 3 times and then he got the message we get when someone rejects the call or the phone is out of battery. I never had a missing call to know that he called back. This is a very tricky error, since maybe you are missing incoming calls from your boss. To you it appears like you never received the call, but to your boss it seems like you are ignoring him. Not a good thing.

2) This is a problem i am getting for the last 2 months. When someone calls and the device is sleeping, i hear the ringing, i unlock the phone but what i get is the main page of the device. No incoming call notification, no dialer, nothing.Only the ringtone. If i press the phone app i get 3 choices:

a) use touch tone keypad
b)return to call in process
c)add call

Pressing "return to call in process" doesnt do a thing. To see who has called you, you must go to the missed calls after the ringing is over. Also if you dont restart the device, the problem stays there. The only solution is to restart the device. After restarting the device the problem goes away for 2-3 days and then it happens again.

I dont know if other Nexus 5 owners are experiencing the same problems, but since a smart phone is based on making and receiving calls, these 2 problems must be addressed by Google ASAP.

Also, i am not willing to factory reset my device, if i am not sure that this will 100% solve the problem.

PS1: My device is NOT rooted.

PS2: My brother's Nexus 4 started having the same problem (problem number 2) after updating to Kit Kat 4.4.2. But not in the same frequency as my Nexus 5.