I have heard from some sources online that they don't properly store some products.
Nothing like unfounded heresay to make your case.
OTOH, I have actually had pcb fab (4 layer) and built (SMT assembly) thru JLCPCB 60 pcs of one design and 50 pcs of another.
On the first assembly, only one board failed after testing, was due to lifted pins on an SMT connector. A little bit of solder touchup and its fixed.
On the second assembly, several boards (3) were damaged during separation from the panelization. It was cosmetic only, did not cause any functional issue.
They offered me a discount coupon on a subsequent assembly run, which I accepted. It more than covered the cost of the three impacted boards.
Being in the USA, the only complaint I have is in the shipping options. Either very slow, and cheap, or very costly, and expensive.
For a small build the shipping cost can match or exceed the cost of the pcb plus assembly. So I have learned to be patient and use slow shipping.
Overall I have absolutely no complaints in using JLCPCB and plan to use them again. So far I have spent in excess of US$500 in total pcb fab and assembly costs.
FYI attached is a picture of the latest board I had built thru JLCPCB.