I'm using SOGo 2.3.3a on a CentOS 6.5 server (using the official SOGo packages).

I started with two contacts in my address book:

BEGIN:VCARD
UID:5281-5657B880-1-2C1A198.vcf
VERSION:3.0
CLASS:PUBLIC
PROFILE:VCARD
N:;Joe Bloggs
FN:Joe Bloggs
EMAIL;TYPE=work:joeblogs@example.com
END:VCARD

and

BEGIN:VCARD
UID:530C-5657B900-1-2A2FE6C0.vcf
VERSION:3.0
CLASS:PUBLIC
PROFILE:VCARD
N:;Sally Bloggs
FN:Sally Bloggs
END:VCARD

The first is synchronized, the second is not.

Here is a full copy of the trace:

[info ] Preparing synchronization
[info ] Querying capabilities
[trace] --> PROPFIND /SOGo/dav/fred@bloggsfamily.id/Contacts/personal/ HTTP/1.1
[trace] Depth: 0
[trace] <?xml version='1.0' encoding='UTF-8' ?><propfind xmlns="DAV:" xmlns:CAL="urn:ietf:par\
[trace] ams:xml:ns:caldav" xmlns:CARD="urn:ietf:params:xml:ns:carddav"><prop><CARD:supported-\
[trace] address-data /><n0:getctag xmlns:n0="http://calendarserver.org/ns/&quot; /></prop></propfi\
[trace] nd>
[trace] --> END PROPFIND (258-byte body)
[trace] <-- HTTP/1.1 207 Multi-Status (1525ms)
[trace] Server: nginx
[trace] Date: Fri, 27 Nov 2015 02:28:08 GMT
[trace] Content-Type: text/xml; charset="utf-8"
[trace] Content-Length: 478
[trace] Connection: keep-alive
[trace] X-Dav-Error: 200 No error
[trace] Ms-Author-Via: DAV
[trace] Pragma: no-cache
[trace] Cache-Control: no-cache
[trace] OkHttp-Selected-Protocol: http/1.1
[trace] OkHttp-Sent-Millis: 1448591287577
[trace] OkHttp-Received-Millis: 1448591287974
[trace] <?xml version="1.0" encoding="utf-8"?>
[trace] <D:multistatus xmlns:a="urn:ietf:params:xml:ns:carddav" xmlns:D="DAV:" xmlns:b="http:\
[trace] //calendarserver.org/ns/"><D:response><D:href>/SOGo/dav/fred@bloggsfamily.id/Contacts/p\
[trace] ersonal/</D:href><D:propstat><D:status>HTTP/1.1 200 OK</D:status><D:prop><b:getctag>1\
[trace] 448591266</b:getctag></D:prop></D:propstat><D:propstat><D:status>HTTP/1.1 404 Not Fou\
[trace] nd</D:status><D:prop><a:supported-address-data/></D:prop></D:propstat></D:response></\
[trace] D:multistatus>
[trace] <-- END HTTP (478-byte body)
[debug] Received <response> for https://sogo.myserver.com/SOGo/dav/fred@bloggsfamily.id/Contacts/personal/, status: null, properties: [getctag(http://calendarserver.org/ns/): GetCTag(cTag=1448591266),
supported-address-data(urn:ietf:params:xml:ns:carddav): null]
[info ] Server advertises VCard/4 support: false
[info ] Processing locally deleted entries
[info ] Locally preparing dirty entries
[info ] Uploading dirty entries
[info ] Checking sync state
[info ] Manual sync, ignoring CTag
[info ] Listing local entries
[debug] Found local resource: 5281-5657B880-1-2C1A198.vcf
[debug] Found local resource: 530C-5657B900-1-2A2FE6C0.vcf
[info ] Listing remote entries
[trace] --> REPORT /SOGo/dav/fred@bloggsfamily.id/Contacts/personal/ HTTP/1.1
[trace] Depth: 1
[trace] <?xml version='1.0' encoding='UTF-8' ?><CARD:addressbook-query xmlns="DAV:" xmlns:CAR\
[trace] D="urn:ietf:params:xml:ns:carddav"><prop><getetag /></prop><CARD:filter /></CARD:addr\
[trace] essbook-query>
[trace] --> END REPORT (184-byte body)
[trace] <-- HTTP/1.1 207 Multi-Status (385ms)
[trace] Server: nginx
[trace] Date: Fri, 27 Nov 2015 02:28:08 GMT
[trace] Content-Type: text/xml; charset="utf-8"
[trace] Content-Length: 761
[trace] Connection: keep-alive
[trace] Cache-Control: no-cache
[trace] Pragma: no-cache
[trace] OkHttp-Selected-Protocol: http/1.1
[trace] OkHttp-Sent-Millis: 1448591288114
[trace] OkHttp-Received-Millis: 1448591288487
[trace] <?xml version="1.0" encoding="utf-8"?>
[trace] <D:multistatus xmlns:D="DAV:" xmlns:C="urn:ietf:params:xml:ns:carddav"><D:response><D\
[trace] :href>/SOGo/dav/fred@bloggsfamily.id/Contacts/personal/5281-5657B880-1-2C1A198.vcf</D:h\
[trace] ref><D:propstat><D:prop><D:getetag>"gcs00000000"</D:getetag><C:address-data>BEGIN:VCA\
[trace] RD
[trace] UID:5281-5657B880-1-2C1A198.vcf
[trace] VERSION:3.0
[trace] CLASS:PUBLIC
[trace] PROFILE:VCARD
[trace] N:;Joe Bloggs
[trace] FN:Joe Bloggs
[trace] EMAIL;TYPE=work:joeblogs@example.com
[trace] END:VCARD</C:address-data><C:addressbook-data>BEGIN:VCARD
[trace] UID:5281-5657B880-1-2C1A198.vcf
[trace] VERSION:3.0
[trace] CLASS:PUBLIC
[trace] PROFILE:VCARD
[trace] N:;Joe Bloggs
[trace] FN:Joe Bloggs
[trace] EMAIL;TYPE=work:joeblogs@example.com
[trace] END:VCARD</C:addressbook-data></D:prop><D:status>HTTP/1.1 200 OK</D:status></D:propst\
[trace] at></D:response></D:multistatus>
[trace] <-- END HTTP (761-byte body)
[debug] Ignoring unknown/unparseable property addressbook-data(urn:ietf:params:xml:ns:carddav)
[debug] Received <response> for https://sogo.myserver.com/SOGo/dav/fred@bloggsfamily.id/Contacts/personal/5281-5657B880-1-2C1A198.vcf, status: null, properties: [address-data(urn:ietf:params:xml:ns:carddav): AddressData(vCard=BEGIN:VCARD
UID:5281-5657B880-1-2C1A198.vcf
VERSION:3.0
CLASS:PUBLIC
PROFILE:VCARD
N:;Joe Bloggs
FN:Joe Bloggs
EMAIL;TYPE=work:joeblogs@example.com
END:VCARD),
getetag(DAV:): GetETag(eTag=gcs00000000)]
[debug] Found remote VCard: 5281-5657B880-1-2C1A198.vcf
[info ] Comparing local/remote entries
[info ] 530C-5657B900-1-2A2FE6C0.vcf is not on server anymore, deleting
[info ] Downloading remote entries
[info ] Downloading 0 contacts (10 at once)
[info ] Saving sync state
[info ] Saving CTag=1448591266