Gitzo Systematic Version/Mark 3, Quality Control Issue?

Hello all,
Thanks for reading all the text, but if you do not wish, you may jump to the last paragraph(SUMMARY).
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Had the chance to test two(2) new samples of GT5533LS.
One was an exchange for the returned first one.
Both was suffering from loose Leg Angle Joints, on arrival, no previous use. Will write details about both at the same time, because both have the same exact problem.
Among six(6) joints, one was really hanging to the spider with no tension at all.
Another joint, has just a good amount of tension that the tripod can be carried by that leg without skidding.
The other four(4) joints, had a minimal tension that was enough only for the legs to be stopped at any angle when splayed on vertical upright position only. The tension was not enough to hold the tripod weight(only or with head) on horizontal position, you can not carry the tripod as usual(folded and un-splayed) by those four legs and walk for a short distance, without skidding of the same leg or other legs.
BTW, to avoid any potential subjective results, the appropriate tension amount was referenced to(compared with) a two(2) years old Gitzo GT4542LS and with a one(1) year old RRS TVC-23 tripods, that did not need any tightening so far. Both came with enough tension in leg angle joints, did not need any further tightening so far. Both used well, but not every day.
Ok, why the leg angle joints has not been tightened in the first place?
Thats the frustrating issue/experience!
While the joints structures had no displacement(slippage) from their position(in the joints) at their minimal tension(good looking, but not good functioning), they do not accept tightening any further. It's nothing more than the tension already brought by the FACTORY, or the joint may lose some tension. Actually, one bolt started to lose its grip from repeating tightening the joint. The magnitude of tightening the joints, is not direct proportionally related to the tension on the legs, as it supposed to be. Every possible way of tightening on every position of the tripod legs/joints, has been performed, but nothing tension, or some thing near nothing tension, has been gained.
The joints axis along the bolt/nut location, looks fixed, deadly fixed, though the joints are not jammed(actually loose). Trying to minimally swing the joints laterally(perpendicular to its normal angle), resulted in apparent distortion of the spider(flex).
Wondering if that is a:
1. Quality control issue with the early batches of that tripod model!; or is it,
2. Usual with Magnesium cast?; or, is it,
3. The tolerance that inevitably skewed due to the paint over the cast(or something else),that may produce a marvelous tripod beside another horrible one(un-tighten-able) in the same batch?; or,
4. What??? Anyway, It's a long journey between the exit door of the factory and the hands of the customer!
The subject may be repeated, sorry if it is repeated. Trying to accumulate the possible reasons for a defective Leg Angle Joint in any tripod of any make or generation, in this thread. Hope that attracts interest in this thread. Carbon Fiber tripods, are so pricy and well adopted by photographers of all generations.
To be fair, I should say: Gitzo has undeniable reputation and long history in tripod making, though still wondering what's behind those two tripods(may be the whole batch) of the same model and generation. But, at the same level of fairness, Gitzo customer service(unfortunately) is another dark planet beyond our solar system.
Thanks too much for your input and for reading. Sorry being long.
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SUMMARY:
A frustrating experience about two(2) samples of Gitzo GT5533LS. Loose leg angle joints, variable degrees of looseness. No matter how much you tighten the joints, It's nothing tension you may gain more than the tension already brought by the FACTORY, or the joint may lose some tension.
Wondering if it's a quality control issue with the early batches of that tripod! Or what?
Thanks.