Probably the web resource was not closed automatically when switching projects. Please check if the last update fixes this issue.
Related bug: I can't close a web resource tab (and only web resource tabs) by right-clicking on its tab, and selecting Close Tab. Previous build.
The new build fixes it.
Hans CafeTran Wiki
A trainee creates a new translation project and makes sure that one of three Linguee web resource definitions (one for each of three languages) in the Dashboard is ticked.
When the new project is created, this web resource get its own pane in the tabbed pane, but also a second tab with the name of this Linguee resource plus a star, is opened.
Why is this.