If EJB invocations can't be completed the ejb-client mark the channel/connection as broken and therefore a hickup is seen in the logfiles. If it is a single server there might be some invocations rejected with an EJBCLIENT000025 failure.
The client should make a difference for logical issues and not invalidate the channel/connection.

The log might show an error and after that the server is not available, the messages look like this:
DEBUG org.jboss.ejb.client.EJBClientContext: MyServer is excluded from handling appname=,modulename=myEJB,distinctname= in invocation context org.jboss.ejb.client.EJBClientInvocationContext@4b66500b

One case is if the worker thread with the invocation was canceled, in that case the Exception is like followed:
2016-07-25 16:03:45,740 DEBUG [pool-1-thread-2] org.jboss.ejb.client: Retrying invocation org.jboss.ejb.client.EJBClientInvocationContext@5160492d which failed on node: v-lau due to:
org.jboss.ejb.client.RequestSendFailedException
at org.jboss.ejb.client.remoting.RemotingConnectionEJBReceiver.processInvocationInternal(RemotingConnectionEJBReceiver.java:257)
at org.jboss.ejb.client.remoting.RemotingConnectionEJBReceiver.processInvocation(RemotingConnectionEJBReceiver.java:215)
at org.jboss.ejb.client.EJBClientInvocationContext.sendRequest(EJBClientInvocationContext.java:184)
......
Caused by: java.lang.InterruptedException
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1301)
at java.util.concurrent.Semaphore.acquire(Semaphore.java:317)
at org.jboss.ejb.client.remoting.ChannelAssociation.acquireChannelMessageOutputStream(ChannelAssociation.java:261)
at org.jboss.ejb.client.remoting.RemotingConnectionEJBReceiver.processInvocationInternal(RemotingConnectionEJBReceiver.java:239)