There is a defect that causes duplicate sets of logs to be created in releases up to 10.4.0. In these releases, the workaround is to specify the file name in the log appender fully, using the built-in logback substitution variable com.tibco.ep.dtm.logging.logDirectory to get the full path of the directory. For example:
<appender name="FILE" class="ch.qos.logback.core.FileAppender">
<file>${com.tibco.ep.dtm.logging.logDirectory}/mylog.log</file>
<encoder>
<pattern>%-5level: %msg%n</pattern>
</encoder>
</appender>