[system test][windows] rebalance failed after failover a node

Environment:
8 nodes physical server with 32 GB RAM each.
Source:
10.2.1.61
10.2.1.62
10.2.1.63

10.2.1.64

Target
10.2.1.65
10.2.1.66
10.2.1.67

10.2.1.68

Couchbase cluster 2.5.1-1070 on both source and target.
Create 3 nodes cluster at each source and target.
Create 2 buckets (9 GB RAM each) with 1 replica on both cluster.
Create unidirection from source to target at both buckets with xdcr set to version 2.
Keys are loaded at source.

After resident ration at source went down under 100%, do access phase in 3 hours.
At source, add node 64 to cluseter => passed.
At source, remove node 63 ==> passed
At source, add back node 63 ==> passed
At source, auto failover node 64 and rebalance => rebalance failed with errors:

Rebalance exited with reason {{badmatch,{error,closed,
[

,

,

,

,

,

,

,

]},
{gen_server,call,
['ns_memcached-sasl-2',

,
180000]}},
{gen_server,call,
[

,

,
infinity]}}

Before this error, I saw other error showing memcached disconnected on node 64

Control connection to memcached on 'ns_1@10.2.1.64' disconnected: {{badmatch,
{error,
closed}},
[

,

,

,

,

,

,

,

]}