query returns incorrect result for table with no PK and non-unique CHAR utf8mb4 SK

mysql> CREATE TABLE t1 (cola char(3) not null, colb char(3) not null, filler char(200), key ka(cola), key kb(colb)) default charset utf8mb4 engine=rocksdb;
Query OK, 0 rows affected, 2 warnings (0.01 sec)

mysql> INSERT INTO t1(cola,colb,filler) VALUES('aaa','aaa', 'Z1'), ('aaa','aaa', 'Z2'), ('aaa','aaa', 'Z3'), ('bbb','bbb', 'Z4');
Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT COUNT(*) FROM t1;
+----------+
| COUNT(*) |
+----------+
|        4 |
+----------+
1 row in set (0.00 sec)

mysql> SELECT * FROM t1;
+------+------+--------+
| cola | colb | filler |
+------+------+--------+
| aaa  | aaa  | Z1     |
| aaa  | aaa  | Z2     |
| aaa  | aaa  | Z3     |
| bbb  | bbb  | Z4     |
+------+------+--------+
4 rows in set (0.00 sec)

mysql> SELECT COUNT(*) FROM t1 WHERE cola = 'aaa';
+----------+
| COUNT(*) |
+----------+
|        3 |
+----------+
1 row in set (0.00 sec)

mysql> SELECT * FROM t1 WHERE cola= 'aaa';
+------+------+--------+
| cola | colb | filler |
+------+------+--------+
| aaa  | aaa  | Z1     |
| aaa  | aaa  | Z2     |
| aaa  | aaa  | Z3     |
+------+------+--------+
3 rows in set (0.00 sec)

mysql> SELECT COUNT(*) FROM t1 WHERE cola <> 'aaa';
+----------+
| COUNT(*) |
+----------+
|        1 |
+----------+
1 row in set (0.00 sec)

mysql> SELECT * FROM t1 WHERE cola <> 'aaa';
+------+------+--------+
| cola | colb | filler |
+------+------+--------+
| aaa  | aaa  | Z1     |    <<<< !!!! WRONG RESULT !!!!
+------+------+--------+
1 row in set (0.00 sec)

mysql> SELECT * FROM t1 FORCE INDEX(kb) WHERE cola <> 'aaa';
+------+------+--------+
| cola | colb | filler |
+------+------+--------+
| bbb  | bbb  | Z4     |
+------+------+--------+
1 row in set (0.00 sec)