role is creating succesfully but cant grant any privilege to it and after flush privileges it gives ERROR 1133 (28000)

Welcome to the MariaDB monitor.  Commands end with ; or \g.

Your MariaDB connection id is 346

Server version: 10.3.12-MariaDB-1:10.3.12+maria~bionic mariadb.org binary distribution

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> create user demo1 identified by '1234';

Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> create role r1;

Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> grant all on *.* to r1;

Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> grant r1 to demo1;

Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> show grants for r1;

+----------------------------+

| Grants for r1              |

+----------------------------+

| GRANT USAGE ON *.* TO 'r1' |

+----------------------------+

1 row in set (0.000 sec)

MariaDB [(none)]> set default role r1 for demo1;

Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> exit

Bye

~$ mysql -u demo1 -p

Enter password: 

Welcome to the MariaDB monitor.  Commands end with ; or \g.

Your MariaDB connection id is 348

Server version: 10.3.12-MariaDB-1:10.3.12+maria~bionic mariadb.org binary distribution

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> show databases;

+--------------------+

| Database           |

+--------------------+

| information_schema |

+--------------------+

1 row in set (0.001 sec)

MariaDB [(none)]> select current_role();

+----------------+

| current_role() |

+----------------+

| r1             |

+----------------+

1 row in set (0.000 sec)

MariaDB [(none)]> show grants for demo1;

+------------------------------------------------------------------------------------------------------+

| Grants for demo1@%                                                                                   |

+------------------------------------------------------------------------------------------------------+

| GRANT r1 TO 'demo1'@'%'                                                                              |

| GRANT USAGE ON *.* TO 'demo1'@'%' IDENTIFIED BY PASSWORD '*A4B6157319038724E3560894F7F932C8886EBFCF' |

+------------------------------------------------------------------------------------------------------+

2 rows in set (0.000 sec)

MariaDB [(none)]> select current_user();

+----------------+

| current_user() |

+----------------+

| demo1@%        |

+----------------+

1 row in set (0.000 sec)