Here is an example: I have selected 11 files. After a few seconds (probably due to tag edit by lyrics lookup), the status bar looks like in the first picture, with the selected file information missing.
When I delete the files, the status bar says I have -10 files selected. Probably it is -11 plus the one file it automatically selects below the deleted files.

I'm on build 3074 non-debug. I can't say if the problem was present on earlier builds.
Let me know if you can reproduce the issue or if I need to provide further information.