I don't know reasons of this failure but I would like to point some issues about this car.
My '92 G200 has 285k Km (177k Miles). I have got it 2.5 years ago for 7k euro after discovering in a plant where she was parked in 2009. In 2 years I have done 7k km replacing a lot of parts starting from shock absorbers, tires, breake oil , disc and shoes breakes, fuel pump, diff lock soft line and diff lock pump, ecc.
I checked damaged parts and they are dated 07/92 (date on blue seal) means that they are 27 years old. I think this could be a normal problem after 27 years of working w/o maintenance. On my VW T5 4motion I have replaced the right CV-Join after 60k Km).
Now I have found all components to repair the left side including a NOS W463 first version wheel hub (the difference is in the fixing screw of the disc breake), complete kit of seals and nuts for CV-Join (516 euro including shipping costs from Germany). I won't replace CV-Join because it is original and in very nice shape, only small scratches on the end of multispline shaft. But I will remove its to replace all seals, grease and to verify plays.
Concerning the loose hub nut, I don't think this could be the reason of the problem. I have good experience in vintage cars because I restore VW T1 and T2 imported from USA (I'm an active member of Thesamba forum) and old Citroen starting from cadavers and the first point normally I check is the play in all directions of the wheels. In the G play was verified immediately after the purchase and was perfect; balance of new tires is near 0.
In my opinion this is a defect of project because torque on left side is higher than right side. I saw this effect in the snow because I use my G to go on my alp refuge during winter. The left wheel turns before the right and I need to engage the diff lock. I haven't this problem on T5.
But, from my side, this is my first experience on MB cars and I have to admit they are really complicates and expencives. Original '60 NOS VW parts are cheaper...
I will update thread with more pics.