Drive Shaft seized on the final drive splines

[mspratz]

UPDATE:
Moreover, there is no groove on the inside teeth of the front coupling, so the circlip only fits into the groove on the spline and relies on a "friction fit" against the teeth of the front coupling ...?

Wayne, I just had a look at the gearbox output shaft in the fiche, and it appears that the groove for the snapring is almost at the very end of the shaft (outlined in red below), with by far the bulk of the splines completely in front of it, so perhaps there is no groove in the inside of the splines of the front end of the driveshaft, because those spines are designed to slide entirely over the snapring.