Ofuscação de Código Java (Proguard)

Boa Tarde,
Quando uso o proguard para realizar a ofuscação de código ele me retorno os seguintes erros:

Reading library jar [C:\mypro\dist\lib\log4j-api-2.11.2.jar]
Warning: class [META-INF/versions/9/module-info.class] unexpectedly contains class [module-info]
Warning: class [META-INF/versions/9/org/apache/logging/log4j/util/StackLocator.class] unexpectedly contains class [org.apache.logging.log4j.util.StackLocator]
Note: duplicate definition of library class [org.apache.logging.log4j.util.StackLocator]
Warning: class [META-INF/versions/9/org/apache/logging/log4j/util/internal/DefaultObjectInputFilter.class] unexpectedly contains class [org.apache.logging.log4j.util.internal.DefaultObjectInputFilter]
Warning: class [META-INF/versions/9/org/apache/logging/log4j/util/ProcessIdUtil.class] unexpectedly contains class [org.apache.logging.log4j.util.ProcessIdUtil]
Note: duplicate definition of library class [org.apache.logging.log4j.util.ProcessIdUtil]
Reading library jar [C:\mypro\dist\lib\log4j-core-2.11.2.jar]
Warning: class [META-INF/versions/9/org/apache/logging/log4j/core/util/SystemClock.class] unexpectedly contains class [org.apache.logging.log4j.core.util.SystemClock]
Note: duplicate definition of library class [org.apache.logging.log4j.core.util.SystemClock]

como posso revolver esse problema na ofuscação de codigo

Desde já agradeço!