had this problem too. it’s definite not notes-related. i resolved it by opening folder in explorer and played around with folder options (applied new setting). sorry, can’t remember what i changed, but it helped…
With your Attach/Detach dialog open, right click somewhere blank in the file selection area in the middle (i.e. not on a file) and click ‘Arrange Icons By > Name’ until your files sort in ascending order again. You must have done this by accident at some point to get them sorting the other way round.