Good news . I received good results from my researches .
Now i have a temporary solution other than resetting (or rebooting) the routeros . The real problem causes by PCQ issue and when user want to disconnect the pppoe and connect again , unregister_netdevice occurs.
The OLD way to solve the unregister_netdevice was reboot but the NEW way is disable and enable all queues (simple queues or queue trees) and then disable and enable radius (if using radius)
We can do this job with a simple script but now the question is this . How we can determine that when unregister_netdevice occurs ? i mean determine unregister_netdevice by script , not by seeing the monitor or winbox . if a script can understand this problem right when the problem occured , it can do the job and problem will be solve .
Please suggest your good ideas.