After upgrading the Apache httpClient to 4.4, I found that other plugins such as Git-Client/Maven-plugin that also uses httpClient with different versions collapses with ours. So After I added the Mask-Classes attribute the problem was gone, but it looks like this isolated environment dose not apply for Slaves.

I found out that in the RemoteClassLoader while it tries to find a specific class URL, Which.classFileUrl(class) uses the getResource method. This method is not override by the hudson.util.MaskingClassLoader. So the class comes from the right source under the plugin itself, but the resource URL of the same class can came from other source such as other plugins that contain the same classes.

Error example that I get:

at hudson.model.Executor.run(Executor.java:240)
Caused by: java.io.IOException: Remote call on local-windows failed
at hudson.remoting.Channel.call(Channel.java:748)
at hudson.FilePath.act(FilePath.java:907)
... 9 more
Caused by: java.lang.NoSuchFieldError: INSTANCE
at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.<init>(DefaultHttpRequestWriterFactory.java:52)
at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.<init>(DefaultHttpRequestWriterFactory.java:56)
at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.<clinit>(DefaultHttpRequestWriterFactory.java:46)
at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.<init>(ManagedHttpClientConnectionFactory.java:72)
at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.<init>(ManagedHttpClientConnectionFactory.java:84)
at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.<clinit>(ManagedHttpClientConnectionFactory.java:59)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager$InternalConnectionFactory.<init>(PoolingHttpClientConnectionManager.java:493)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.<init>(PoolingHttpClientConnectionManager.java:149)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.<init>(PoolingHttpClientConnectionManager.java:138)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.<init>(PoolingHttpClientConnectionManager.java:114)
at org.apache.http.impl.client.HttpClientBuilder.build(HttpClientBuilder.java:726)
at org.jfrog.build.client.HttpClientConfigurator.getClient(HttpClientConfigurator.java:91)
at org.jfrog.build.client.ArtifactoryHttpClient.getHttpClient(ArtifactoryHttpClient.java:140)
at org.jfrog.build.client.ArtifactoryHttpClient.execute(ArtifactoryHttpClient.java:209)
at org.jfrog.build.client.ArtifactoryHttpClient.upload(ArtifactoryHttpClient.java:205)
at org.jfrog.build.extractor.clientConfiguration.client.ArtifactoryBuildInfoClient.uploadFile(ArtifactoryBuildInfoClient.java:603)
at org.jfrog.build.extractor.clientConfiguration.client.ArtifactoryBuildInfoClient.deployArtifact(ArtifactoryBuildInfoClient.java:315)
at org.jfrog.hudson.generic.GenericArtifactsDeployer$FilesDeployerCallable.deploy(GenericArtifactsDeployer.java:179)
at org.jfrog.hudson.generic.GenericArtifactsDeployer$FilesDeployerCallable.invoke(GenericArtifactsDeployer.java:151)
at org.jfrog.hudson.generic.GenericArtifactsDeployer$FilesDeployerCallable.invoke(GenericArtifactsDeployer.java:119)
at hudson.FilePath$FileCallableWrapper.call(FilePath.java:2484)
at hudson.remoting.UserRequest.perform(UserRequest.java:118)
at hudson.remoting.UserRequest.perform(UserRequest.java:48)
at hudson.remoting.Request$2.run(Request.java:328)
at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at hudson.remoting.Engine$1$1.run(Engine.java:63)
at java.lang.Thread.run(Thread.java:744)