md here means markdown, this file is likely the note itself (the markdown content without the external resources), 22128dd155db4b4caeb5571f7cdf9b49 is likely the note id
what happens when you search for 22128dd155db4b4caeb5571f7cdf9b49 directly in joplin? can you identify the note?
if you can find the note, try duplicating it (right click, duplicate), then delete the old copy, empty trash, restart app, sync, does it help?
if nothing helps, export your whole dataset as jex file and start over, follow the guide: How to fix synchronisation issues and start over