A lot of this thread has been people arguing about their personal belief whether the OP was trust worthy, and speculating on other people's motivation/logic to believe or dismiss the rumor, is there really any point along this line of argument?
Instead, I'd like to hear some discussion towards trying to ballpark the likelihood and the impact. Below are my guesses:
1) what's the chance the rumor is real? 10%? 20%? 50%? There was one case back in MX days that such warning turned out to be real, so I would guess <50%, maybe <<50%?
2) what's the chance that the problem can't be solved in 5 months before mass release happens? If it's in the electrical system and the fault is supposedly caused by simplification of MS/MX so a working baseline exist, and they just need to find what changed. This is much easier to trouble shoot than for example the FWD where they didn't have a working baseline to start with. I think the chance is good that they can find and fix the problem in 5 months, I would put that at >50%, maybe >>50%.
3) what are the alternatives if they can't fix it in 5 months? I can think of a few, they don't so bad, especially if you look ahead into 2018
a) hold off delivering 10% of cars that are faulty until a fix is found, and also set aside some $ to fix cars that passed initially but showed problems later on
b) roll back to MS/MX design and take a hit on manufacturing/tooling cost temporarily, change it back to the simplified version 1-2 quarters later when a fix is found
c) delay mass release until the issue is fixed, lets say another quarter, this gives 8 months to fix a problem
So in summary, I see the rumor as having low likelihood to be real, with a good chance that it will be fixed before mass release, and even in the worst case it impacts mass release, there are contingencies that are not temporary speed bumps, but no more