Vexinor
Beware from export/import implementation of contacts. I said that I transferred 100% of contacts through vcf file.
Later, I noticed fault and I'm still frustrated several months later, today. I actually have 100% of contacts (Hurray for me. right?)...but while importing vcf, you can't trust the GOS that it show the right count of contacts either. The import vcf function shows my 1352 contacts count, but that is only how many contacts are there as unique and that's not right either. I lived with that I have all contacts correctly transferred and as time passes, I add several more, time to time I edited the old ones thinking everything is good and then the breakthrough incident appeared when I wanted to edit another old contact. I found one particular and clicked the pencil to edit and GOS showed unexpected pop up: "Choose contact to edit:" where was that same contact listed several times! WTF? I had that vcf file I exported several months earlier and I started to probing it with python what's inside. There wasn't 1352 contacts as I expected, but over 3000! One contact was unique, other was there several times. OK, minor bug, I thought. I started to create python script to de-duplicate that but, God, that was mess. I still don't have any clue how to identify the duplicity. The contact that appear in GOS as duplicity, one had note, other don't or had part of it, one had 3 numbers, other duplicity two with third missing. Total mess. If unique contact have 8 duplicates and you want to look on number, or note, you can't notice that you looking on several duplicates at once. GOS somewhat shows all that duplicates at once and it looks right as single contact until you want to edit. Now my script has 400 lines of code and I'm far from finishing it because I want to compare other entries like photo data and so on but I found out that photos was also re-processed and there is also unique contact that have same looking photo, but photo is stored as different photo data and I can't distinguish which one is original. I'm also pissed because GOS show me that contact have several duplicates, but there is no function how to select particular one to delete it. I'm close to give up, and manually rewrite all of it that will take many hours.
taivlam
considering that faults starts to appear mainly while restoring or after restore, your post is actually not useful at all.