Strange Cubase 13 not releasing files after close

Windows 10, Cubase 13.0.3.

I was trying to update my Kazrog Avalon VST3 plugin via their installer. The installer failed with an access denied error.

I went to the folder where the VST3 file is stored and tried to delete the VST3 file. Windows said it was open by Cubase 13. Cubase 13 was not running, and not showing in Task Manager.

So I started Cubase and then closed it. No difference.

Then I started Cubase and killed the process in Task Manager. No difference.

I had to restart the computer in order to delete the file.