This doesn't happen to me on macOS 10.12.4 with Script Debugger 6.0.5 (6A203).
However – there is an oddity...
As you can see in the first image the name is not fully visible in the tab. (The tab was created with Cmd-Shift-T.)
The next tab (created in the same fashion) shows the complete title.
If I create another one it WON'T show the complete title.
If I create another one it WILL show the complete title.
Something's just a bit off there...