Ok so I haven’t seen anything like this happen in any app before so it was really baffling when it did in BSS. I was about to save a project with a new name so I could play with some new features and such and not worry about messing up a production site.
I highlighted a few characters that I wanted to delete from the design name and when I went to delete them, instead it was deleting things from my project that I had selected (in this case some CSS files). I say File(s) plural because I didn’t notice what it was doing at first since everything is kind of made foggy looking behind the Save As dialog so when I did notice I realized it was deleting the one originally selected and of course I hit the delete button more than once thinking it wasn’t working … and it was selecting the next CSS file below the last one deleted and so on and so on.
So I Undid the deletions with the dialog window still open (clicked it to be sure it was in focus) for Save As using Ctrl+z and of course it undid the changes that were made to the project, which once again it shouldn’t be doing with the Save As window in focus, not sure on this part though if that might be ok, seems it might be.
I then used the Backspace button and that worked to delete what I was trying to delete in the dialog window.
I then tried putting the cursor in front of what I wanted to delete and tried deleting the characters one by one with the delete key and again it deleted what I had selected in the project window instead.
So the moral of the story is … Delete is not working correctly with dialog boxes open (might be other things too? that’s for you to find lol) Hope this helps! Hope it gets fixed soon as well because with this UNDO issue I’m having, I’d hate to think I would delete a bunch of files and not realize it right away and then not be able to Undo them all 
