Nexus 5 Marshmallow incoming call screen

[fhutt1]

My contact settings include photos in the phone app. I believe I am using the contacts in the phone, not the SIM card.
When people with pictures in the contacts call me their caller ID and number are shown on the incoming call screen but not their photo.
I cannot find any settings for the incoming call screen on the default phone app or my 3rd party app (PixelPhone).
Could someone please help me include the photos of contacts on the incoming call screen?
Thanks

Edit: Just noticed that a picture is indeed showing but it is so dark that I didn't notice it before. However, I also notice on the picture there is a work written saying "Unknown" in the middle of the picture. What does that mean?

 

[fhutt1]

Just updated the stock Phone app and the picture now shows correctly.
However, the sticking problem of the "Unknown" is still shown.
I have attached a screenshot of the phone's call screen showing the picture and the word "Unknown" in the middle". I have blurred the phone number and street name.
Hope this helps someone point me to find the cause of this.