A bit of a discovery on my particular generation of this error "cannot_finish_ui_if_not_setting_ui"
I have the topcoll format installed and the mdl_format_topcoll_settings table was not present (as I updated to Moodle 2.6 from 2.3)
Sometimes the "mdl_format_topcoll_settings table missing" error was generated with debugging turned on; sometimes the error "cannot_finish_ui_if_not_setting_ui" occurred when trying to backup a course.
I created a new table in the database using the following and my backups work fine now.
SET NAMES utf8;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for `mdl_format_topcoll_settings`
-- ----------------------------
DROP TABLE IF EXISTS `mdl_format_topcoll_settings`;
CREATE TABLE `mdl_format_topcoll_settings` (
`id` bigint(10) NOT NULL AUTO_INCREMENT,
`courseid` bigint(10) NOT NULL,
`layoutelement` tinyint(2) NOT NULL DEFAULT '1',
`layoutstructure` tinyint(1) NOT NULL DEFAULT '1',
`layoutcolumns` tinyint(1) NOT NULL DEFAULT '1',
`tgfgcolour` varchar(6) NOT NULL DEFAULT '000000',
`tgbgcolour` varchar(6) NOT NULL DEFAULT 'e2e2f2',
`tgbghvrcolour` varchar(6) NOT NULL DEFAULT 'eeeeff',
PRIMARY KEY (`id`)
) ENGINE=`InnoDB` AUTO_INCREMENT=1 DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci ROW_FORMAT=COMPACT COMMENT='States the settings used with the given course.' CHECKSUM=0 DELAY_KEY_WRITE=0;
SET FOREIGN_KEY_CHECKS = 1;
If using topcoll format in your course(s), check to see if the table exists, and if not, create the table, then try your backup!