Error " java.rmi.RemoteException: Unable to locate cache server" in Slave Server Manager log and requests are responding slowly in Windchill

ERROR [ServerManagerRegistryPinger] wt.cache.server.wt.manager.jmx.ServerManagerRegistry - caught cache server call exception
java.rmi.RemoteException: Unable to put remote cache entry; nested exception is: 
    java.rmi.RemoteException: Unable to locate cache server; nested exception is: 
    wt.util.WTRemoteException: Unable to get server; nested exception is:
    java.rmi.ConnectException: Connection refused to host: <hostname>; nested exception is: 
    java.net.ConnectException: Connection refused: connect
    at wt.cache.RemoteCacheServer.putEntryInternal(RemoteCacheServer.java:404)
    at wt.cache.RemoteCacheServer.lambda$putEntry$19(RemoteCacheServer.java:333)
    at wt.cache.RemoteCacheServer.callTimeAndLogRemoteCallableLow(RemoteCacheServer.java:680)
    at wt.cache.RemoteCacheServer.callTimeAndLogRemoteCallable(RemoteCacheServer.java:652)
    at wt.cache.RemoteCacheServer.putEntry(RemoteCacheServer.java:330)
    at wt.cache.CacheManager.put(CacheManager.java:943)
    at wt.cache.CacheManager.put(CacheManager.java:931)
    at wt.manager.jmx.ServerManagerRegistry.pingMasterAndSlaves(ServerManagerRegistry.java:178)
    at wt.manager.jmx.ServerManagerRegistry$RegistryPinger.run(ServerManagerRegistry.java:322)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.rmi.RemoteException: Unable to locate cache server; nested exception is: 
    wt.util.WTRemoteException: Unable to get server; nested exception is:
    java.rmi.ConnectException: Connection refused to host: <hostname>; nested exception is: 
    java.net.ConnectException: Connection refused: connect
    at wt.cache.RemoteCacheServer.getCacheServer(RemoteCacheServer.java:630)
    at wt.cache.RemoteCacheServer.putEntryInternal(RemoteCacheServer.java:392)
    ... 15 more
Caused by: wt.util.WTRemoteException: Unable to get server; nested exception is:
    java.rmi.ConnectException: Connection refused to host: <hostname>; nested exception is: 
    java.net.ConnectException: Connection refused: connect
    at wt.manager.RemoteServerManager.remoteInvoke(RemoteServerManager.java:486)
    at wt.manager.RemoteServerManager.getServer(RemoteServerManager.java:278)
    at wt.manager.RemoteServerManager.getServer(RemoteServerManager.java:262)
    at wt.cache.RemoteCacheServer.getCacheServer(RemoteCacheServer.java:610)
    ... 16 more
Caused by: java.rmi.ConnectException: Connection refused to host: <hostname>; nested exception is: 
    java.net.ConnectException: Connection refused: connect
    at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:619)
    at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:216)
    at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202)
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:129)
    at wt.manager.ServerManagerImpl$MasterServerManagerImpl_Stub.getServer(Unknown Source)
    at wt.manager.RemoteServerManager.lambda$getServer$28(RemoteServerManager.java:279)
    at wt.manager.RemoteServerManager.remoteInvoke(RemoteServerManager.java:449)
    ... 19 more
Caused by: java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at java.net.Socket.connect(Socket.java:538)
    at java.net.Socket.<init>(Socket.java:434)
    at java.net.Socket.<init>(Socket.java:211)
    at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:40)
    at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:148)
    at wt.boot.WrappedRMIDirectSocketFactory.createSocket(WrappedRMIDirectSocketFactory.java:28)
    at wt.boot.WTRMIMasterSocketFactory.createSocket(WTRMIMasterSocketFactory.java:194)
    at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613)