Recently it has been found on platform x86 pppoe-users dont logout when there is a disconnection in physical connectivity (router reboot etc). You have to manually disconnect from winbox. Earlier I thought its the becoz of memory consumption. As it happened on one of the MT running 6.44.2 but today it happened to another MT today running 6.45.6 with 28 days of uptime with free memory 1400mb. Already sent the support file for 6.44.2 but couldnt make on the other one.