The Sleeve issue may or may not be related.
And while I cannot tell from the pics what is wrong there has been at least one Member who had a loose Collar Nut and the on the female side of the Coupling were eaten up.
Or maybe the Collar Nut is simply loose.
Nice pics.
Maybe the U-joint needs to be beaten on as in the below thread.
Sticking U-joint causes Vibration that Rips up several Drive Shaft Supports turns out to be Rusty Needle Bearings
W123 Propeller shaft vibration tears up rubber mounts, replaced nearly everything