Seems to be a limitation due in how we are calling ttyd?
If we add a salt (time) to the object name like the vanilla webterminal does (which allows multiple sessions), that should get around the issue?
openTerminal('ttyd','Web Terminal '+d.getTime(),'');
If that's not possible, I did find a workaround, it looks like you can use simply use the URL to create as many new sessions as you want, i.e. http://jaskier.local/logterminal/DiskSpeed/ creates a new terminal session, its just not as elegant as using the GUI as we do now.