“signer information does not match […]” error within an Eclipse bundle

Question

I got the security issue with a big Eclipse plugin Maven project, which uses Xtext, Xtend and fornax-oaw-m2-plugin (which fails). I extracted the used classpath, and searched in there if the incriminated class is present in at least two jars, but no. It is only present in one bundle. Could I grab more information into the stacktrace? I could provide many more information.. I google since two days and not found interesting clue so far. As the class in in an Eclipse bundle, i can't change it safely..

[INFO] Caused by: org.eclipse.emf.common.util.WrappedException: java.lang.SecurityException: class "org.eclipse.emf.ecore.impl.MinimalEObjectImpl$Container"'s signer information does not match signer information of other classes in the same package.

Here is the project's MANIFEST.MF :

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: com.mds.regseq
Bundle-Vendor: Magillem Design Services S.A.S.
Bundle-Version: 1.0.0.qualifier
Bundle-SymbolicName: com.mds.regseq; singleton:=true
Bundle-ActivationPolicy: lazy
Require-Bundle: org.eclipse.xtext;bundle-version="2.3.1";visibility:=reexport,
 org.apache.log4j;visibility:=reexport,
 org.apache.commons.logging;resolution:=optional;visibility:=reexport,
 org.eclipse.xtext.generator;resolution:=optional,
 org.eclipse.emf.codegen.ecore;resolution:=optional,
 org.eclipse.emf.mwe.utils;resolution:=optional,
 org.eclipse.emf.mwe2.launch;resolution:=optional,
 org.eclipse.xtext.util,
 org.eclipse.emf.common,
 org.antlr.runtime,
 org.eclipse.xtext.common.types,
 com.mds.spiritschema.xmlfactory,
 com.mds.mrv;visibility:=reexport,
 com.mds.regseq.mrv.binding;visibility:=reexport
Import-Package: org.apache.commons.logging,
 org.apache.log4j, org.eclipse.emf.ecore
Export-Package: com.mds.regseq,
 com.mds.regseq.formatting,
 com.mds.regseq.interpreter,
 com.mds.regseq.parseTreeConstruction,
 com.mds.regseq.parser.antlr,
 com.mds.regseq.parser.antlr.internal,
 com.mds.regseq.properties,
 com.mds.regseq.register_sequencing,
 com.mds.regseq.register_sequencing.impl,
 com.mds.regseq.register_sequencing.util,
 com.mds.regseq.scoping,
 com.mds.regseq.services,
 com.mds.regseq.type,
 com.mds.regseq.util,
 com.mds.regseq.validation
Bundle-RequiredExecutionEnvironment: JavaSE-1.6