You can hit enter and the command repeats, so you can then select the lines for filleting, yesno?
Assuming it used to stay in the command instead of returning to the command line, I would suspect a system variable OR something in a registry value has changed. Have you recently used a registry cleaner other than the windows one? Or have you recently installed or updated a Norton (Symantec) product?
I hope my info was useful, but if by some odd chance it actually solved your issue, feel free to mark your post as "Accept as Solution". Thanks! 🙂