Import fails due to Error running user management migration task

2014-05-23 16:45:01,020 JiraImportTaskExecutionThread-1 INFO liam 1002x243x1 ow5a02 117.104.180.121,165.254.226.65 /secure/admin/StudioImport!import.jspa [importer.impl.user.JiraUserServiceImpl] Running user management migration task
May 23, 2014 4:45:01 PM com.sun.jersey.server.impl.application.WebApplicationImpl _initiate
INFO: Initiating Jersey application, version 'Jersey: 1.8-atlassian-13 01/23/2014 06:03 AM'
2014-05-23 16:45:01,605 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] Rolling back User Management. Disabling the dark feature
2014-05-23 16:45:01,614 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.downgrade.unlicensed: [daniel, tony@8hq.co.nz, wei, tom, jason, jon]
2014-05-23 16:45:01,614 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.existing.use.groups: null
2014-05-23 16:45:01,614 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.existing.use.users: null
2014-05-23 16:45:01,614 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.existing.admin.groups: null
2014-05-23 16:45:01,614 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.existing.admin.users: null
2014-05-23 16:45:01,614 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.existing.site-admins: null
2014-05-23 16:45:01,614 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.chosen.users: null
2014-05-23 16:45:01,614 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.chosen.admins: null
2014-05-23 16:45:01,615 TP-Processor3 WARN      [usermanagement.userprovisioning.spi.AbstractUpgradeService] unified.admin.migration.chosen.site-admins-backup: null
2014-05-23 16:45:01,617 TP-Processor3 ERROR      [common.error.jersey.ThrowableExceptionMapper] Uncaught exception thrown by REST service: Backup values were stored incorrectly. Some values were null. See logs above.
java.lang.RuntimeException: Backup values were stored incorrectly. Some values were null. See logs above.
      at com.atlassian.crowd.plugin.usermanagement.userprovisioning.spi.AbstractUpgradeService.logAllPreviousUseAndAdminGroups(AbstractUpgradeService.java:273)
      at com.atlassian.crowd.plugin.usermanagement.userprovisioning.spi.AbstractUpgradeService.doDowngrade(AbstractUpgradeService.java:127)
      at com.atlassian.crowd.plugin.usermanagement.userprovisioning.MigrationResource.undoUpgrade(MigrationResource.java:81)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
      at java.lang.reflect.Method.invoke(Method.java:597)
      at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
      at com.sun.jersey.server.impl.model.method.dispatch.VoidVoidDispatchProvider$VoidVoidMethodInvoker._dispatch(VoidVoidDispatchProvider.java:71)
      at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
      at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288)
      at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
      at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
      at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
      at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469)
      at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400)
      at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
      at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
      at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
      at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
      at com.atlassian.plugins.rest.module.RestDelegatingServletFilter$JerseyOsgiServletContainer.doFilter(RestDelegatingServletFilter.java:178)
      at com.sun.jersey.spi.container.servlet.ServletContainer.doFilter(ServletContainer.java:795)
      at com.atlassian.plugins.rest.module.RestDelegatingServletFilter.doFilter(RestDelegatingServletFilter.java:73)
      at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter.doFilter(DelegatingPluginFilter.java:74)
      at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:42)
      at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.java:77)
      at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.java:63)
...