In the configuration screen for the Advanced Search block in the islandora_solr_search module (#overlay=admin/islandora/search/islandora_solr/settings) and the "Advanced search block" and 'Sort" tabs changes to permissions in the configure option are not being saved.
Pull request has a fix for this bug. The issue was in the _islandora_solr_handle_solr_field_settings function. The cases for sort and search fields both lack a permissions_enabled option in the configuration options so they were both not holding the permissions when they were changed. The permissions check was just changed from $solr_field_settings['permissions_enabled'] (which was always false) to just $solr_field_settings['permissions']. The options for permissions are getting saved on change now.