I’m a technical writer and could write a book on this subject but I'll give you the abridged version of my experience. All the warnings come from the lawyers of course, and those are nonnegotiable. If legal says you have to do something then you have to do it no matter how little sense it may make IRL.
As to consumer manuals in general, most are bad because companies don't want to pay for a writer/editor. They figure anyone can write (how hard could it be?) so when a product ships they usually give that job to a dev volunteer, or maybe even a marketing droid or someone in support. There are various problems with this, but one of the biggest with devs is that they don't know the product. Sure, they know their one little area very well, but the whole thing as an assembled, functioning unit? They're clueless. That's not meant to be a slam because if you design taillights for Chevy why would you know or care about how the transmission works, or how to even drive a car for that matter. The other problem is they universally cannot write. They always think they can, but that goes back to thinking anyone can write. There are college degrees given in the subject for a reason, so this makes as much sense as thinking someone can be an architect simply because they live in a house. The third is companies are lazy and just don't care, and I see this all the time. For example, there's one major tractor company that right now has multiple grammar and punctuation errors in their two page online sales pdf. How many people had to check off on that before it went out? How expensive would it have been to have one of those people be a trained editor who understood the English language? Not very. Another good example is all those manuals for stuff from Harbor Freight. Is it really that hard or expensive to hire someone who's a native English speaker to give those a quick edit/translation? Of course not, but they don't because manuals are an afterthought and nobody cares.
All that is for companies that don't have pro writers on staff. For those that do, there's a whole other assortment of problems that get introduced but I'll leave all that boring stuff for another day.