Why are my contacts disappearing from my S5?

[AC Question]

Contacts disappearing from S5

Since yesterday I noticed that contacts are disappearing from my phone.
The call log only mentions the phone number, no longer the associated contact.
Sometimes I still find a contact with the contacts email-address but not his phone number.

I see no logic in the contacts that are disappearing, it just seem some random contacts. I probably only notice a few of them like the ones that are in my log or like today in my favorites as they catch attention rapidly.

I have synchronisation with Facebook, Whatsapp and LinkedIn (and due to the LinkdIn synchronisation I had a lot of doubles so I disabled that a few weeks ago) but this cannot explain everything as one of the contacts that disappeared today is my grandmother who is 95 and she is not on LinkedIn, FB or whatever social network.

I'm on Android 5.0. For what I've know there hasn't been any update recently to the Android system. Recent updated apps are Messenger & Twitter.

I tried installing Contacts+ but the contacts are not appearing in there either. They are not completely gone however as I can all find them when I look online (contacts.google.com). Anybody has a clue about what's going on?

Would I be able to do a complete restore from contacts.google.com?

 

[Wolfenfang]

Having the same issue as of this evening. Went to call my dad and realized his number was missing, I'd called him last night no problem. Many other numbers are missing including my husband's and grandparent's!