You can block spammer based on IP/port filter rules or you can "play" with
/ip firewall layer7-protocol http://wiki.mikrotik.com/wiki/Manual:IP/Firewall/L7
and, maybe, some scripts.
I use IP address. This problems is on remote servers.VARELA, looks like you are using MAC address to connect. This is a very slow and unreliable method of communication, and many items are loaded slowly.
Use IP address and check if you have the same problem.
Because terminal is not working I attach screenshotsplease to enable ssh topic in logging, or ssh,debug topics for more details on ROS end.
But local machine is MikroTik - base station, and need connect to client MT.You can write expect script that will connect to routers from specific address list and execute needed commands.