Unknow error in debug.log with java SDK NullpointException from time to time

I have an error message in debug.log and don't know what it mean.

=========================PROGRESS REPORT=========================
supervisor:

{local,menelaus_sup}
started: [{pid,<0.16556.158>},
{name,menelaus_web_alerts_srv},
{mfargs,{menelaus_web_alerts_srv,start_link,[]}},
{restart_type,permanent},
{shutdown,5000},
{child_type,worker}]

[error_logger:error,2015-08-25T11:11:43.930,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:do_log:203]OS_MON (memsup) called by <0.308.0>, not started

[error_logger:error,2015-08-25T11:11:43.930,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:do_log:203]OS_MON (memsup) called by <0.308.0>, not started

[error_logger:error,2015-08-25T11:11:43.930,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:do_log:203]OS_MON (disksup) called by <0.308.0>, not started

[error_logger:error,2015-08-25T11:11:44.320,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:do_log:203]OS_MON (disksup) called by <0.16599.158>, not started

[error_logger:error,2015-08-25T11:11:44.320,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:do_log:203]
=========================SUPERVISOR REPORT=========================
Supervisor: {local,menelaus_sup}

Context: child_terminated
Reason: {{badmatch,none},
[{menelaus_web_alerts_srv,'check/4-lc$^1/1-2',2,
[

{file,"src/menelaus_web_alerts_srv.erl"},{line,245}]},
{menelaus_web_alerts_srv,check,4,
[{file,"src/menelaus_web_alerts_srv.erl"}

,

{line,244}]},
{lists,foldl,3,[{file,"lists.erl"},{line,1248}]},
{menelaus_web_alerts_srv,'handle_info/2-fun-0',2,
[{file,"src/menelaus_web_alerts_srv.erl"},
{line,170}]}]}
Offender: [{pid,<0.16556.158>},
{name,menelaus_web_alerts_srv},
{mfargs,{menelaus_web_alerts_srv,start_link,[]}},
{restart_type,permanent},
{shutdown,5000},
{child_type,worker}]


[error_logger:error,2015-08-25T11:11:44.320,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:do_log:203]Error in process <0.16599.158> on node 'ns_1@127.0.0.1' with exit value: {{badmatch,none},[{menelaus_web_alerts_srv,'check/4-lc$^1/1-2',2,[{file,"src/menelaus_web_alerts_srv.erl"},{line,245}]},{menelaus_web_alerts_srv,check,4,[{file,"src/menelaus_web_alerts_srv.erl"},{line,244}

]},{lists,foldl...

[error_logger:info,2015-08-25T11:11:44.320,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:do_log:203]

It occur every second.
I don't konw whether it is because to kill the process memcached.
I kill the process is because to NullpointException in Spring-Data-Couchbase 1.3.2.RELEASE and it use couchbase-cleint 1.4.7,memcached 2.11.6

java.lang.NullPointerException: null
at net.spy.memcached.internal.OperationFuture.getCas(OperationFuture.java:226) ~[spymemcached-2.11.6.jar:2.11.6]
at org.springframework.data.couchbase.core.CouchbaseTemplate$4.doInBucket(CouchbaseTemplate.java:317) ~[spring-data-couchbase-1.3.2.RELEASE.jar:na]
at org.springframework.data.couchbase.core.CouchbaseTemplate$4.doInBucket(CouchbaseTemplate.java:299) ~[spring-data-couchbase-1.3.2.RELEASE.jar:na]
at org.springframework.data.couchbase.core.CouchbaseTemplate.execute(CouchbaseTemplate.java:244) ~[spring-data-couchbase-1.3.2.RELEASE.jar:na]
at org.springframework.data.couchbase.core.CouchbaseTemplate.save(CouchbaseTemplate.java:299) ~[spring-data-couchbase-1.3.2.RELEASE.jar:na]
at org.springframework.data.couchbase.core.CouchbaseTemplate.save(CouchbaseTemplate.java:149) ~[spring-data-couchbase-1.3.2.RELEASE.jar:na]
at org.springframework.data.couchbase.repository.support.SimpleCouchbaseRepository.save(SimpleCouchbaseRepository.java:82) ~[spring-data-couchbase-1.3.2.RELEASE.jar:na]
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source) ~[na:na]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.7.0_60]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.7.0_60]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:434) ~[spring-data-commons-1.10.2.RELEASE.jar:na]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:419) ~[spring-data-commons-1.10.2.RELEASE.jar:na]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:391) ~[spring-data-commons-1.10.2.RELEASE.jar:na]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.1.0.RELEASE.jar:4.1.0.RELEASE]
at org.springframework.data.couchbase.repository.support.ViewPostProcessor$ViewInterceptor.invoke(ViewPostProcessor.java:87) ~[spring-data-couchbase-1.3.2.RELEASE.jar:na]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.1.0.RELEASE.jar:4.1.0.RELEASE]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-4.1.0.RELEASE.jar:4.1.0.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.1.0.RELEASE.jar:4.1.0.RELEASE]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207) ~[spring-aop-4.1.0.RELEASE.jar:4.1.0.RELEASE]
at com.sun.proxy.$Proxy59.save(Unknown Source) ~[na:na]

OperationFuture.java:226
This line a global variable status is null when specific save method in my code with crudRepository and other will not

So I have to kill the memcached process and it will restart itself then it would become work fine

In the end, the disk overview in the console cannot show correctly

Is there any recommendation to deal with it or any more info I can provide.
Or I just try to reinstall the couchbase because other machine do not have those problems in the same version.

Sorry for my poor English.