Thread.sleep

I have quite a few of these in the stderrr file.
any though what this might mean?
(system config below)

Java.lang.Thread.sleep(Native Method)
lucee.runtime.schedule.ScheduledTaskThread.sleepEL(ScheduledTaskThread.java:166)
lucee.runtime.schedule.ScheduledTaskThread._run(ScheduledTaskThread.java:127)
lucee.runtime.schedule.ScheduledTaskThread.run(ScheduledTaskThread.java:88)
28-Jul-2016 22:37:04.736 WARNING [127.0.0.1-startStop-2]
org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The
web application [ROOT] appears to have started a thread named [Thread-54]
but has failed to stop it. This is very likely to create a memory leak.
Stack trace of thread:
java.lang.Thread.sleep(Native Method)===========
General Info

Version
Lucee 4.5.2.018 final

OS
Windows Server 2012 R2 (6.3) 64bit

Servlet Container
Apache Tomcat/8.0.28

Java
1.8.0_91 (Oracle Corporation) 64bit

Architecture
64bit