Is it possible that your computer is slow to respond to open the file so you decide to click on it a second time to open it in the belief that the first 'open' did not work? This second 'Open' command for the same file will give the issue you are having. Sometimes impatience, nervous fingers and double-click can give these issues. I know. I have done it myself.

Try waiting a bit longer to see if the file opens at first attempt.