getting one of those "failed to serialize" exceptions that seem to be reported everywhere re: the jep-200 change, with respect to the matrix reloaded plugin.  this plugin is not listed at https://wiki.jenkins.io/display/JENKINS/Plugins+affected+by+fix+for+JEP-200, however when I uninstalled it, all the issues  was having went away.

the stack trace is below, and along with it, a successful matrix build fails to set itself as "successful" in some way, e.g. the junit.xml doesn't get written and it the lastSuccessfulBuild symlink seems to get reset, I don't know how all these things work but that's the handwavy summary.

SEVERE: Failed to save build record
java.io.IOException: java.lang.RuntimeException: Failed to serialize hudson.model.Actionable#actions for class hudson.matrix.MatrixRun
at hudson.XmlFile.write(XmlFile.java:200)
at hudson.model.Run.save(Run.java:2015)
at hudson.model.Run.execute(Run.java:1876)
at hudson.matrix.MatrixRun.run(MatrixRun.java:153)
at hudson.model.ResourceController.execute(ResourceController.java:97)
at hudson.model.Executor.run(Executor.java:429)
Caused by: java.lang.RuntimeException: Failed to serialize hudson.model.Actionable#actions for class hudson.matrix.MatrixRun
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:256)
at hudson.util.RobustReflectionConverter$2.visit(RobustReflectionConverter.java:224)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.visitSerializableFields(PureJavaReflectionProvider.java:138)
at hudson.util.RobustReflectionConverter.doMarshal(RobustReflectionConverter.java:209)
at hudson.util.RobustReflectionConverter.marshal(RobustReflectionConverter.java:150)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:69)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:43)
at com.thoughtworks.xstream.core.TreeMarshaller.start(TreeMarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.marshal(AbstractTreeMarshallingStrategy.java:37)
at com.thoughtworks.xstream.XStream.marshal(XStream.java:1026)
at com.thoughtworks.xstream.XStream.marshal(XStream.java:1015)
at com.thoughtworks.xstream.XStream.toXML(XStream.java:988)
at hudson.XmlFile.write(XmlFile.java:193)
... 5 more
Caused by: java.lang.UnsupportedOperationException: Refusing to marshal net.praqma.jenkins.plugin.reloaded.MatrixReloadedAction for security reasons; see https://jenkins.io/redirect/class-filter/
at hudson.util.XStream2$BlacklistedTypesConverter.marshal(XStream2.java:546)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:69)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:43)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:88)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeItem(AbstractCollectionConverter.java:64)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.marshal(CollectionConverter.java:74)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:69)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:84)
at hudson.util.RobustReflectionConverter.marshallField(RobustReflectionConverter.java:265)
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:252)
... 18 more