Please upload a sogo.log after doing this:

• Set SOGoEASDebugEnabled = YES
• Create a contact on your S6.
• After it has synced to the server update the contact on the server.

Does your S6 show the update?
What are the differences of the 2 contacts which are synced compared to others?

I create a new contact on the sogo web frontend and this contact getting synced to the S6 and Outlook every time.
If i change this contact on the S6 everything is synced back to Outlook and sogo.
It makes no difference on which devices I change the contact after the contact is synced for the first time and local on the device the changes now are replicated to all other devices.
Now i added contacts in Outlook (completely new) --> everything synced also to the S6.
This is how it should work and it works when i add completely new contacts.

This is how i can produce the issue:
Copy about 10 or more contacts via Outlook or Thunderbird to the contacts, they are getting synced to the sogo server so you can see them in the web frontend. There were not getting synchronized to other devices like my S6. Iphones can find the contacts, sometimes thunderbird also didn´t find them. It seems that some devices (S6) doesn´t see contacts copied to sogo. But are visible in the sogo web frontend.
Now when i change a contact in the Sogo web frontend for example an additional "a" to the name, the contact is getting synced to the S6 and thunderbird.
I tried many different contacts, some with a lot of information and some with only the name. This makes no difference; I think the problem is about copying contacts trough ActiveSync. Sogo does not replicate them to other devices but sogo shows changes made on other devices.
I hope you can understand and reproduce it.

Produce a sogo.log with SOGoEASDebugEnabled = YES:
-Copy e.g. 10 contacts
-Synchronize your S6 and iPhone
-Change a contact on the server
-Synchronize your S6 and iPhone

I upload the sogo.log

Sorry, the logfile contains too many activities to analyze. I count alot of additions from both sites. Please split/reduce the size and explain what you did and when.

Have you set "SOGoMaximumSyncWindowSize" in sogo.conf?
If yes, remove it and re-test.

I have remove "SOGoMaximumSyncWindowSize" in sogo.conf.
Now i copy 9 contacts trough Outlook in the empty default contacts folder.
But only 2 contacts are synced to sogo webfrontend AND this contacts are synced to the S6!
What is with the other 7 contacts?
I Upload a new sogo.log starting from the Outlook copy action.

What I see in the logfile confirms your findings, that sogo received ONLY 2 contacts from outlook and they are synced to your S6.
The problem migth be related to what has been repored in bug 3928.
Can you please try to copy another contact to the contacts folder and let me know the result?

Your are right. :)
After copy the 9 contacts to the contact folder only 2 contacts are synced.
Copy 1 addidional contact to the contact folder all 10 contacts are synced to sogo and the S6!
Strange thing.
Is this an sogo or Outlook bug?

IMHO the wrong behavior is caused by outlook. SOGo can only process what it receives in the requests from OL.

I suggest we write a FAQ entry about this and close both issues (perhaps even refer to the bug IDs in the FAQ entry.

@tfu, are you up to write a small FAQ entry for this?

Thanks!

Is it possible this bug is a timing problem from the sogo EAS Server?
But an FAQ entry would be nice.

I stumbled upon this thread after encountering the very same problem. After some experimenting I found out that (at least in my situation) this only occurs for contacts that have been imported.

I migrated to a new mailserver and so I exported the contacts on the old one and imported them again on the new server. None of them were synced to my samsung devices (S5 and TabS). When creating a new contact on either the sogo web-interface or any samsung device, the contact was synced just fine.

I hope this info may prove usefull in some way.

Cheers!