websphere8.5 500错误

4个节点，3个都是好的，就一个后台报错。代码都是同步的。很郁闷。
ctrl+f5刷新页面又可以访问了，但是总是有些文件没下载下来，样式和js这些。
之前也遇到过，特别是压力测试后，然后重启机器就会好的。
现在重启机器也不行。
[13-10-14 18:42:47:023 CST] 00000117 webapp        E com.ibm.ws.webcontainer.webapp.WebApp logServletError SRVE0293E: [Servlet 错误]-[Static File wrapper]: java.lang.NullPointerException

at com.happ.CompressionServletResponseWrapper.flushBuffer(CompressionServletResponseWrapper.java:171)

at com.ibm.ws.webcontainer.servlet.FileServletWrapper.handleRequest(FileServletWrapper.java:510)

at com.ibm.ws.webcontainer.servlet.StaticFileServletWrapperImpl.handleRequest(StaticFileServletWrapperImpl.java:150)

at com.ibm.ws.webcontainer.extension.DefaultExtensionProcessor.handleRequest(DefaultExtensionProcessor.java:717)

at com.ibm.ws.webcontainer.filter.WebAppFilterChain.invokeTarget(WebAppFilterChain.java:136)

at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:97)

at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:195)

at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:91)

at com.jh.jcs.framework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:64)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:195)

at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:91)

at com.happ.CompressionFilter.doFilter(CompressionFilter.java:122)

at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:195)

at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:91)

at com.ibm.ws.webcontainer.filter.WebAppFilterManager.doFilter(WebAppFilterManager.java:928)

at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:1025)

at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3761)

at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:304)

at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:975)

at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1662)

at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:195)

at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:459)

at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:526)

at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:312)

at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.ready(HttpInboundLink.java:283)

at com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.sendToDiscriminators(NewConnectionInitialReadCallback.java:214)

at com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.complete(NewConnectionInitialReadCallback.java:113)

at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)

at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)

at com.ibm.io.async.AsyncChannelFuture$1.run(AsyncChannelFuture.java:205)

at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1815)