You are right we are not trying to promote to a release repo using staging. Here is a debug log
com.sonatype.nexus.api.exception.RepositoryManagerException: Unable to upload component: Forbidden <html>
10:32:21 <head>
10:32:21 <title>403 - Forbidden</title>
10:32:21 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
10:32:21
10:32:21 <link rel="icon" type="image/png" href="http://***********:8082/nexus/favicon.png">
10:32:21 <!--[if IE]>
10:32:21 <link rel="SHORTCUT ICON" href="http://***********:8082/nexus/favicon.ico"/>
10:32:21 <![endif]-->
10:32:21
10:32:21 <link rel="stylesheet" href="http://************:8082/nexus/static/css/Sonatype-content.css?2.13.0-01" type="text/css" media="screen" title="no title" charset="utf-8">
10:32:21 </head>
10:32:21 <body>
10:32:21 <h1>403 - Forbidden</h1>
10:32:21 <p>Forbidden</p>
10:32:21 </body>
10:32:21 </html>
10:32:21
10:32:21 at com.sonatype.nexus.api.db.a(SourceFile:37)
10:32:21 at com.sonatype.nexus.api.df.a(SourceFile:73)
10:32:21 at com.sonatype.nexus.api.df.a(SourceFile:46)
10:32:21 at com.sonatype.nexus.api.df.uploadComponent(SourceFile:27)
10:32:21 at com.sonatype.nexus.api.dc.uploadComponent(SourceFile:78)
10:32:21 at com.sonatype.nexus.api.repository.RepositoryManagerClient$uploadComponent.call(Unknown Source)
10:32:21 at org.sonatype.nexus.ci.nxrm.ComponentUploader$_uploadComponents_closure2.doCall(ComponentUploader.groovy:93)
10:32:21 Caused: java.io.IOException
10:32:21 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
10:32:21 at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
10:32:21 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
10:32:21 at java.lang.reflect.Constructor.newInstance(Unknown Source)
10:32:21 at org.codehaus.groovy.reflection.CachedConstructor.invoke(CachedConstructor.java:83)
10:32:21 at org.codehaus.groovy.runtime.callsite.ConstructorSite$ConstructorSiteNoUnwrapNoCoerce.callConstructor(ConstructorSite.java:105)
10:32:21 at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:247)
10:32:21 at org.sonatype.nexus.ci.nxrm.ComponentUploader$_uploadComponents_closure2.doCall(ComponentUploader.groovy:96)
10:32:21 Caused: java.io.IOException: Upload of BMS2WebEar/build/libs/BMS2WebEAR.ear failed
10:32:21 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
10:32:21 at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
10:32:21 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
10:32:21 at java.lang.reflect.Constructor.newInstance(Unknown Source)
10:32:21 at org.codehaus.groovy.reflection.CachedConstructor.invoke(CachedConstructor.java:83)
10:32:21 at org.codehaus.groovy.runtime.callsite.ConstructorSite$ConstructorSiteNoUnwrapNoCoerce.callConstructor(ConstructorSite.java:105)
10:32:21 at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:255)
10:32:21 at org.sonatype.nexus.ci.nxrm.ComponentUploader$_uploadComponents_closure2.doCall(ComponentUploader.groovy:108)
10:32:21 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
10:32:21 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
10:32:21 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
10:32:21 at java.lang.reflect.Method.invoke(Unknown Source)
10:32:21 at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
10:32:21 at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
10:32:21 at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:294)
10:32:21 at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1022)
10:32:21 at groovy.lang.Closure.call(Closure.java:414)
10:32:21 at groovy.lang.Closure.call(Closure.java:430)
10:32:21 at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2040)
10:32:21 at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2025)
10:32:21 at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2066)
10:32:21 at org.codehaus.groovy.runtime.dgm$162.invoke(Unknown Source)
10:32:21 at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:274)
10:32:21 at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:56)
10:32:21 at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
10:32:21 at org.sonatype.nexus.ci.nxrm.ComponentUploader.uploadComponents(ComponentUploader.groovy:77)
10:32:21 at org.sonatype.nexus.ci.nxrm.ComponentUploader$uploadComponents.call(Unknown Source)
10:32:21 at org.sonatype.nexus.ci.nxrm.NexusPublisherBuildStep.perform(NexusPublisherBuildStep.groovy:55)
10:32:21 at hudson.tasks.BuildStepCompatibilityLayer.perform(BuildStepCompatibilityLayer.java:81)
10:32:21 at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
10:32:21 at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:744)
10:32:21 at hudson.model.Build$BuildExecution.build(Build.java:206)
10:32:21 at hudson.model.Build$BuildExecution.doRun(Build.java:163)
10:32:21 at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:504)
10:32:21 at hudson.model.Run.execute(Run.java:1724)
10:32:21 at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
10:32:21 at hudson.model.ResourceController.execute(ResourceController.java:97)
10:32:21 at hudson.model.Executor.run(Executor.java:421)