I wasn't able to reproduce this issue internally. Was this during normal daily compilation, or did you compile your packages in any kind of rapid succession (perhaps accidentally pressing F9 twice)? I'm not sure what would have caused this issue.
For now, you can right-click on the "Errors" tab and select "Close All Tabs", which will close them all and recreate the "Errors" tab (which is the only persistent tab in that window). If you do that, see if you're able to reproduce it again; and if so, let me know the steps you took so we can try to reproduce it here as well.