Typing too fast, strange hidden characters
Your option + space combination defaults to a non-breaking space and several options to remove that binding exist.


https://superuser.com/questions/78245/how-to-disable-the-option-space-key-combination-for-non-breaking-spaces


Whether you choose to show invisible characters in your  editor to manually proof for these issues or use a lint type tool or change the behavior of the system depends on whether you can avoid typing that combination after knowing it exists.