PPPoE terminating - packet drops, CPU heavily loaded

Good afternoon! There is one problem: when the PPPoE session is broken, packets are lost or the response time is greatly increased even between the addresses of the router connected to this. The problem manifests itself at 1800+ sessions, at the ROS 6.35, 6.40.4, 6.39.3. CCR1036, CCR1072 / If you disconnect more sessions at the same time - CPU 100% is downloaded and the traffic volume for the remaining sessions drops sharply. Sorry for my English

Have a look at this
http://forum.mikrotik.com/t/high-cpu-load-when-pppoe-sessions-disconnects/105999/22