Crash on FULLTEXT+UNION search with paritioned table

SELECT gb_id 

FROM gen_idx_birth6 

WHERE MATCH(gb_names_a ) AGAINST ( 'kosk' IN BOOLEAN MODE )

  AND MATCH(gb_names_b ) AGAINST ( 'kwit' IN BOOLEAN MODE )

UNION ALL

SELECT gb_id

FROM gen_idx_birth6

WHERE MATCH(gb_names_b ) AGAINST ( 'kosk' IN BOOLEAN MODE )

  AND MATCH(gb_names_a ) AGAINST ( 'kwit' IN BOOLEAN MODE )

CREATE TABLE `gen_idx_birth6` (

  `region` int(11) NOT NULL,

  `gb_id` bigint(6) NOT NULL,

  `gb_names_a` varchar(100) DEFAULT NULL,

  `gb_names_b` varchar(30) DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3 COLLATE=utf8mb3_polish_ci

PARTITION BY LIST (`region`)

(

PARTITION p7 VALUES IN (7) ENGINE=InnoDB

);

ALTER TABLE `gen_idx_birth6`

  ADD PRIMARY KEY (`gb_id`,`region`) USING BTREE;

ALTER TABLE `gen_idx_birth6` ADD FULLTEXT KEY `ix_names_b` (`gb_names_b`);

ALTER TABLE `gen_idx_birth6` ADD FULLTEXT KEY `ix_names_a` (`gb_names_a`);

ALTER TABLE `gen_idx_birth6`

  MODIFY `gb_id` bigint(6) NOT NULL AUTO_INCREMENT;

COMMIT;