The D40 chassis seems flawed, add a bit of corrosion and it snaps. Some say the corrosion comes from impurities within the metal.
The dates of Navaras affects by chassis problems seem to be getting later and later as newer vehicles show corrosion. Nissan initially blamed it on towbar issues and perhaps it was related. With FB etc I doubt if they can keep a lid on this much longer. "You are the only one with the problem", won't work anymore.
I have a Spanish built Navara manufactured Dec 2012. My mate also purchased one at the same time also. After 2 weeks I noticed corrosion underneath. Every nut and bolt had a crust on it like it had been under sea water for a few years. A certain amount happens and is accepted due to the trip over due to sea water exposure. With a bit of trouble it cleaned off.
I purchased a borescope from Tradetools and could see evidence of rust inside the chassis rails. Each service I asked about this rust but no comments or acknowledgement was ever printed on the Nissan receipts. The local Nissan service agent had his own ideas and wanted to use rust converter which I resisted as if can cause extreme rust later on.
Eventually the Nissan service agents did use Rust Converter against my wishes (and Nissans) and without notifying me. The initial result is no rust, looks nice. However it is starting to come back as you would expect.
After a year I became frustrated with Nissans rubbish and used Consumer Affairs in a case against Nissan. This is the only evidence I have that the vehicle was rusty on delivery. Taking this action means I have a better case against Nissan when the chassis breaks. After submitting the claim Nissan still would not use the word rust or corrosion and referred to the rust issue as Mr xxx's problem.
My mate ran some wires through the chassis of his D40 which unexpectedly forced out large amounts of rust, it was very bad. He had the vehicle for 3 months at the time. Nissan replaced his D40.
My guess is that all D40's are affected, but most people will think it's not going to happen to me and just sit back and watch - well best of luck and keep your seat belts done up tight.