Ubuntu ubuntu-other

Finally I found solution to this problem. I switched from Gnome classic (fallback, flashback) to Mate desktop environment. There it works fine.

Not quite. The file is already open by the program. Deleting the file ( and then replacing it with another version ) does not affect the running program because the original file is held open...

It should be as simple as making a copy of the file. Then, if something goes wrong, you can just delete your modified file and rename the copy.

I would do:

sudo cp...