Contacts disappear and phone restarts when making a call

Help Fairphone 2
1

Hello all,

So, I’ve just starting using my Fairphone 2, and I have had two recurring problems:

  1. A lot of times when I try to make calls, when pressing call, the phone just restarts. Then it turns on again, and in contacts it appears as if I had actually made the call. After that I can normally make the call to that contact, but the same happens if I try to contact someone else.

  2. When I add two numbers to 1 contact, the contact dissapears after a while.

Any ideas?