RADIUS radtest fails to transmit org while radclient works

Good evening,
Kept looking around, and now playing with radius.
I've been able to connect with radclient but not radtest yet.
Here is the working command:
echo "User-Name=admin,class=built-in,User-Password=123" | radclient 127.0.0.1 auth testing123
Tried the usual ways (built-in/admin...) but unable to use the class argument under radtest. Did I miss something to make it work?
Thanks in advance.
EDIT: for instance, radtest -t pap built-in/admin 123 localhost 1812 secret
Appears in log as 2024/03/07 17:05:47 handleAccessRequest() username=built-in/admin, org=, password=123 (clearly, org not transmitted)
and result as Received Access-Reject Id 138 from 127.0.0.1 to 127.0.0.1:48544 length 20
(0) -: Expected Access-Accept got Access-Reject
Edit2: from what i read in the code in radius/server.go, the character "/" should work. But it's does not seem to. Can you guess why ?
if strings.Contains(username, "/") {
organization, username = util.GetOwnerAndNameFromId(username)
}
Using the latest casdoor on nextcloud's hub. (not AIO, regular version)

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