Problem with special login

Hello. We are trying to use “special login” feature for managing devices via com port of rb411u (os v 6.15). All works great, except one thing… When someone forgets to log off from com port another person can’t use the same “special login” because of an error - “error opening serial port, already used by special-login (6)”. So is there a way to force log off such users?

up..