Sometimes query data get null value with GetView<xxx>(...) and return false value with StoreJson(Add, id, object)

I got this problem sometimes in a day(everyday, in many diffence PCs). I made some load tests with 10k transactions/per time and I found that the failure rate of 2% of the total transaction(null value with GetView and false value with StoreJson) of course the data persisted in storage.
You could use this reference service to test: http://123.31.10.239:8082/services.svc
SendRequest("token", "user00", "12345678", "serviceId", "C101", "", byte[0], ref retObj);

sucess value: 00;f4c0d......
failed value: 01; or "Ko co gi!"

I used .Net SDK 2.0.3 in DAL with Shared Connection pattern(singleton with dotNet Remoting), Couchbase Server 3.0.1 CE, 1 data bucket, total 4385 items.
Server specification:
+ CPU: Intel Xeon E312x 2.Ghz (8 processors)
+ RAM: 16Gb
+ OS: Windows Server 2008 R2 Ent, 64 bit.
+ Hdd: 180Gb

I attached DAL project with this ticket for more detail, I used a windows service to call DAL via .net Remoting(singleton pattern).

Hope to get soon your feedback.