I upgraded a RB3011 to 6.39.1, it was 6.37.5.
After the upgrade, everytime a CPE disconnect and connect again the PPP/PPPoE dont send the deauth info to FreeRadius and dont free the IP that the CPE was using, so after the CPE login again the get a new IP and the IP he was using still remaing on the sql table.
To solve the problem I downgraded to 6.37.5 again, and now working fine.
Sorry my english.