From pppoe they problems are already from over 200 active users, from some time.
1) ghost inteface.
2) users cannot login when it is more than 200 active, after reboot.
It in my case helps (on point 2), if switch off interface on which PPPoE is Server, reboot Mikrotik, and I after reboot will include this interface again, customers log in correctly, and cpu utilization is OK.
I sended already some time this and all necessary data, to support, and I wait on improvement ( she had to be in version 2.9.32, and in extra pppoe package)