Index use with collation utf8mb4_unicode_nopad_ci on LIKE pattern with wrong results

CREATE TABLE `aaa` (

	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,

	`a` VARCHAR(50) NOT NULL COLLATE 'utf8mb4_unicode_nopad_ci',

	`b` VARCHAR(50) NOT NULL COLLATE 'utf8mb4_unicode_ci',

	PRIMARY KEY (`id`),

	INDEX `a` (`a`),

	INDEX `b` (`b`)

)

COLLATE='utf8mb4_nopad_bin'

ENGINE=InnoDB

;

INSERT INTO `aaa` VALUES (1, '123', '123');

SELECT * FROM netcon_fahrzeug.aaa WHERE a LIKE '123%'

SELECT * FROM netcon_fahrzeug.aaa IGNORE INDEX (a) WHERE a LIKE '123%'

SELECT * FROM netcon_fahrzeug.aaa WHERE b LIKE '123%'