It does look as if the rear shaft/tube has been welded to the U joint when it should be pinned (parts 9 and 10). I believe the tube is a Europa only part and not available form generic sources. I've no idea how/if it could be repaired. I wonder if you need this adjustment point or if adjustments can be made solely at the connection between the front tube and the U joint? Certainly you need to be sure all of the connections and bushings (bottom of the shift lever, center joint, and rear of trans) are tight in order to shift well.
Thinking about this more..... the pinned connection while not permanent, is not really adjustable. I'd think only one side of the U joint needs to be adjustable and that would be the side where you have the jamb nut. I can't see why the weld would need to be put back to original, unless the U joint needs replacing (the U joint seems to be one of the more robust parts of the system and is likely fine).