menu Window shows wrong active Window

I work on a project for which I sometimes save versions, just to make sure I can get back to a state where everything worked fine so far. So the app.settings stay the same, just the name changes and of course the code.
I noticed some strange behavior when I have two versions open: under menu Window always the wrong file is checked. So if I have version ‘V12’ as active Window, ‘V11’ is checked. And vice versa. It’s just annoying, a bug maybe?
Version 2017.3 for Mac OSX

Yes, it is a bug