Ok, you may need to run slapd under debug mode (-1) and then try binding as one of the users with userPassword set to the {SASL}username@realm value to see what it's doing.
Is this what I did in my first post (https://lists.openldap.org/hyperkitty/list/openldap-technical@openldap.org/t..., the log is at the end of the message) or is there some missing information ?
By the way, I don’t know why GMail is starting a new thread each time I answer to you… :-/