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