when I run the Tomcat shutdown script, Camunda sometimes shuts down as expected and sometimes logs the following message:

30-Apr-2019 15:30:10.349 SEVERE [main] org.apache.catalina.startup.Catalina.stop Catalina.stop
org.apache.catalina.LifecycleException: Failed to stop component [StandardServer[8005]]
at org.apache.catalina.util.LifecycleBase.handleSubClassException(LifecycleBase.java:441)
at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:267)
at org.apache.catalina.startup.Catalina.stop(Catalina.java:755)
at org.apache.catalina.startup.Catalina.start(Catalina.java:717)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:350)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:492)
Caused by: java.lang.NoClassDefFoundError: org/camunda/bpm/engine/impl/SchemaOperationProcessEngineClose
at org.camunda.bpm.engine.impl.ProcessEngineImpl.close(ProcessEngineImpl.java:143)
at org.camunda.bpm.container.impl.jmx.services.JmxManagedProcessEngineController.stop(JmxManagedProcessEngineController.java:41)
at org.camunda.bpm.container.impl.jmx.MBeanServiceContainer.stopService(MBeanServiceContainer.java:124)
at org.camunda.bpm.container.impl.deployment.StopProcessEnginesStep.stopProcessEngine(StopProcessEnginesStep.java:58)
at org.camunda.bpm.container.impl.deployment.StopProcessEnginesStep.performOperationStep(StopProcessEnginesStep.java:46)
at org.camunda.bpm.container.impl.spi.DeploymentOperation.execute(DeploymentOperation.java:119)
at org.camunda.bpm.container.impl.jmx.MBeanServiceContainer.executeDeploymentOperation(MBeanServiceContainer.java:159)
at org.camunda.bpm.container.impl.spi.DeploymentOperation$DeploymentOperationBuilder.execute(DeploymentOperation.java:215)
at org.camunda.bpm.container.impl.tomcat.TomcatBpmPlatformBootstrap.undeployBpmPlatform(TomcatBpmPlatformBootstrap.java:100)
at org.camunda.bpm.container.impl.tomcat.TomcatBpmPlatformBootstrap.lifecycleEvent(TomcatBpmPlatformBootstrap.java:65)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:123)
at org.apache.catalina.util.LifecycleBase.setStateInternal(LifecycleBase.java:424)
at org.apache.catalina.util.LifecycleBase.setState(LifecycleBase.java:367)
at org.apache.catalina.core.StandardServer.stopInternal(StandardServer.java:786)
at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:257)
... 8 more
Caused by: java.lang.ClassNotFoundException: org.camunda.bpm.engine.impl.SchemaOperationProcessEngineClose
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)