Debian 8 prevents the NAS to generate data volume accounting

[oatech]

Something strange is happening :

While the Windows 10 client does have a valid accounting stop message 
generated, with proper data accounting values ( Acct-Input-Packets, 
Acct-Output-Packets, Acct-Input-Octets, Acct-Output-Octets), the Debian 8 
client always have 0 in each of these fields. Ex :

sudo cat /var/log/freeradius/radacct/192.168.1.2/detail-20160324 | grep 
Acct-Input-Octets
        Acct-Input-Octets = 43976
        Acct-Input-Octets = 845
        Acct-Input-Octets = 394240
        Acct-Input-Octets = 0
        Acct-Input-Octets = 371260
        Acct-Input-Octets = 0

( Here, Windows 10 gets proper values recorded, Debian 8 always gets 0 )

Does anybody understand what may cause Debian 8 to prevent data accounting ?
I'm using a very standard Freeradius/MySQL setup ...

Clients :         Windows 10 / Debian 8
NAS :            Cisco SB WAP121
RADIUS Server :        Debian 8 / FreeRADIUS Version 2.2.5, for host 
x86_64-pc-linux-gnu,
Authentication :    PEAP/MSCHAPv2 


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