Yep the small clip that goes in the grove has come off so that the stepped washer that locates on it to stop the shaft going past the mounting point as you can see, always looked a bit feeble to me but not had any problems on mine even as they are revalved so need more grip.
Did that happen whilst driving Cue? It looks like rust where the little circlip goes, maybe it rusted off? When i fitted mine I was dubious about that little circlip taking the strain.