Presumably this file originated on a non-Windows system. Deleting or renaming it there should clear it.
I know you say it doesn’t exist anywhere; nonetheless we have an entry for it that says it should be synced, so it ought to exist somewhere… Syncthing doesn’t have the imagination to make it up on its own.
Your ignore patterns are complicated and, I think, not correct. I’d be more direct, something like Structure and??Interpretation??of Computer ??Programs.pdf, if you want to go that route. (Copy/paste of file name, question marks to match the forbiddens.) The pattern needs to match the entire file name.
I actually don’t know where it originated. It doesn’t exist so cannot be deleted or renamed.
I didn’t suggest Syncthing made it up at all. When I say the file doesn’t exist anywhere I mean it doesn’t exist, anywhere. The file is not on any device. It may have been in the past but it doesn’t exist now.
That makes it no longer flag up as an issue. How do I get rid of it completely without adding that pattern to every ignore file?