In the case of the e-liquid, if I use certain flavorings, and the flavoring manufacturer changes the recipe and informs me, I should pass on that information. If they don't inform me, I should probably be sampling my product at times throughout my process for QC. If it just slips past me and what you received is not what you reasonably expected to receive, that too is my responsibility, thought it may not be my fault.
I think if a flavoring is changed at the chemical level and one thing is substituted for another, then I doubt M/V would share this with the customer. Some might, I think most wouldn't. Especially if it were thought to not affect flavor. You know the DA thing is occurring to me as I write this. Though that does affect flavor, and that would very likely be communicated in today's vaping market. But if it were some other chemical, and it wasn't perceived to affect flavor, I think it might not be communicated up front.
I feel like in my years of vaping that vendors change recipes fairly often and that it is either never communicated or rarely. I actually think lots of businesses that are selling things with flavor might not communicate the change or would promote it if they really wanted it to be known (a la New Coke).
As for mechanical wear and tear. If something functions as it should when purchased, and then wears out, that's not necessarily a defect. Even if it was designed to be made of cheap materials that will only last for X amount of days, that is not a defect, it's underhanded and shameful but that's something altogether different.
I'd like to address this further while trying to get back to topic of the thread. But alas, I'm not up to speed with mechanical specs for more advanced gear. So, let's say a Provari is understood to last about 3 years, and I get one and it last me 6 months before it stops working. Setting aside discussion of it being under warranty and I get it replaced, I'm saying that without an obvious flaw presented to me (or say vendor when I take it to them and show them) that this is not manufacturer's responsibility for the defect. And that wonderful customer service by M/V would likely lead to me getting replacement, but that doesn't mean for me that they admit they did something wrong. Nor should they.
In terms of safety, almost all the cases I've seen (of exploding batteries) has shown up as (most likely) user error. I don't get that impression from media, but from the folks here, and these good folks strike me as around 100 times more knowledgeable than pretty much anyone in the media. Yet, media presents it as defective product some of the time, while mostly spinning it, IMO, as vaping is inherently dangerous, or really as inherently defective.
I know I agree with @Bad Ninja in this thread who again strikes me as far more knowledgeable than anyone in media. I don't necessarily or immediately think of exploding battery as user error, but in almost all instances I'm aware of it strikes me as user was irresponsible in the situation that lead to the battery exploding.