Last thing, just after the upload of attachment, i see this in my log :
08-06 18:33:42.078 20646-28932/com.xxxxxx.xxxxxxW/com.couchbase.lite﹕ Sync: Error converting lastSequence: null to long. Using 0
08-06 18:33:42.088 20646-28930/com.xxxxx.xxxxxW/com.couchbase.lite﹕ Sync: com.couchbase.lite.replicator.PullerInternal@42643840: starting ChangeTracker with since=null mode=OneShot
08-06 18:33:42.088 20646-28930/com.xxxx.xxxxW/com.couchbase.lite﹕ Sync: com.couchbase.lite.replicator.PullerInternal@42643840: started ChangeTracker com.couchbase.lite.replicator.ChangeTracker@42b4ef78
08-06 18:33:42.339 20646-28923/com.xxxx.xxxxW/com.couchbase.lite﹕ Sync: com.couchbase.lite.replicator.PullerInternal@42643840: Received invalid doc ID from _changes: {seq=3825, id=_user/BlueberryHill2015_7_6_1438878751447, changes=[]}
08-06 18:33:42.349 20646-28938/com.xxxx.xxxxE/com.couchbase.lite﹕ Sync: PullerInternal stopGraceful.run() finished