Your question Nr 1: The 1,000 hours Master Control is just focused on the movement, that's why external issue can happen?
My answer: No ,the 1 000 Hours control is not about the movement, but about the whole watch, the movement being tested IN the watch, while, with the COSC, the movement is tested alone.
Your question Nr 2: According to the JLC's manuals, this Control is more strict or demanding than COSC, but according to this test and my experience (I own a NS), caliber 899 should be improved. Do you recommend me to send it my watch in order to improve their rate? I don't have a machine to measure variations precisely, but my perceptions is that my watch performs very similar than the watch tested by WatchTime team. Or...it's caliber 899 normal performance?
My answer: The Cal 899 has alway been submitted to the 1000 Hours Control. Now, if your watch doesn't behave within the 1000 Hours specs, so yes, you should send your watch to set it again.
Try, before, to check each day, on a wholme week, to measure it to check its accuracy. Then report your results to your AD when you send the watch, if you have to send it. How do you know your watch is behaving strangely? Is it running too slow, too fast each day? What are the results?
Any watchmaker can work on a perception, nobody can judge from a preception, but from some objective facts ( sorry for the redundance ).
Your question Nr 3: I have heard and read may negative comments about this collection, do you think JLC should reconsider their continuance?
Many? In terms of quality or in terms of marketing?
Let's say it straight: JLC never claimed that this watch was in dotation at the US Navy SEALs corp.
The SEALs are acting like a laboratory, here.
It may please to some, and it may not for others. As always, should I say, which is the case for every watch.
Why did you get one? Because of the SEALs, or because the watch is a cool watch?
Because of others opinion, or because of your own opinion?
More generally, how many watches had issues, iut of the total production of NS or NSAs?
I will give you another example: I had a Patek 5712. After two weeks, the crown stayed stuck between my fingers when I wound it. And the self winding mechanism was not very efficient, therefore, the power reserve was much shorter than the regular 48 hours.
It happened to other 5712s. Is it enough to say that the watch is not a good one?
Certainly not.
Issues may happen. What does matter is the behaviour of the brand to solve it.
Best,
Nicolas