[Couchbase Server 4.5 DP] XDCR very slow

Couchbase Server
1

I have a Couchbase Server 3.1.0 on Ubuntu 12.04.5 LTS 64bit.
and I have installed Couchbase Server 4.5.0 DP on Ubuntu 12.04.5 LTS 64bit.
I want to do test on XDCR(From CB 3.1.0 to CB 4.5.0 DP).
My source bucket has 5990 docs.
and My XDCR Configuration as follows:

My source bucket DCP Queues as follows:

My Target OS Resource consumption as follows:

Target Bucket Analytics as follows:

Now one hour passed, only 498 docs synced.

2

I do it again, and all works fine.
bath from CB 3.1.0 to CB 4.5Dp and from CB 4.1.0 to CB 4.5DP.