After updating to the latest Dev. channel build, I cannot delete (when pressing the Delete button) multiple files when going going to the temp folder, %temp% folder, prefetch folder by typing it from run or even my own folder on the desktop. Never happened in previous builds. Anyone facing the issue? I believe this is a new bug.
Dev builds are under testing and development, you may try update it and see if the problem persists? Try restart your PC and try again. Most likely, it is a bug and make sure report it by the Feedback Hub app.