When you press the key bound to cycle the tabs CTRL-PageDown by default say and you have MiscCycleTabs=FALSE and you are at the last tab already then it outputs characters to the terminal ";5~" It would be nice if it suppressed such output.
This bug was wrongly affected to xfce4-terminal. I can't reassign it to Terminal.
Sorry, wrong product in bugzilla and a lack of bugzilla permissions mean I can't fix it.