It seems to be a bug, which is being solved. If the feature is necessary for your use case, please check this test firmware. However, keep in mind that this revision is specifically created as a hotfix, and thus, some other features might not work until it is included in the upcoming major release.
If the issue is still present, please revert to the latest official firmware, replicate the issue then generate a troubleshoot file and attach it by editing your question. To generate the file, access router's WebUI, go to System -> Administration > Troubleshoot section and download troubleshoot file from there.