Problem in hostname matching when using regex (%) for user authentication

Apparently backend usernames whose hostname is a regex ending with % are not authenticated via maxscale while they work with direct connection.
Proxy protocol is in use, name resolution controlled via hosts file.
skip_name_resolve=off everywhere.
To be confirmed but the bug seems to show up depending on the actual hostname substring.
An overview:

MariaDB [(none)]> select user,host from mysql.user where user like 'test0%';

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

| User   | Host            |

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

| test03 | da1.%           | BAD

| test04 | da_.example.com | OK

| test05 | da%             | BAD

| test06 | da1%            | BAD

| test07 | da%example.com  | OK

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

They all login OK directly to MariaDB.

Please see test in attached file.